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logarithm/281174: solve 1/4 = 4with the exponent k + 5
1 solutions

Answer 204263 by josmiceli(9645) About Me  on 2010-03-15 17:08:20 (Show Source):


Miscellaneous_Word_Problems/281171: Find three consecutive odd integers such that four times the sum of the last two is two greater than ten times the first.
1 solutions

Answer 204259 by josmiceli(9645) About Me  on 2010-03-15 17:03:06 (Show Source):
You can put this solution on YOUR website!
The consecutive odd integers are:
n
n%2B2
n+%2B+4
given:
4%2A%28n%2B2+%2B+n+%2B+4%29+=+10n+%2B+2
4%2A%282n+%2B+6%29+=+10n+%2B+2
8n+%2B+24+=+10n+%2B+2
2n+=+22
n+=+11
n+%2B+2+=+13
n+%2B+4+=+15
The numbers are 11,13, and 15
check:
4%2A%28n%2B2+%2B+n+%2B+4%29+=+10n+%2B+2
4%2A%2811%2B2+%2B+11+%2B+4%29+=+10%2A11+%2B+2
4%2A28+=+110+%2B+2
112+=+112
OK


Average/281164: Helping my son, 7th grade. We need help please.
Q- average for five quizzes is 86. To have an average of 88 or more for six quizzes, what is the lowest score to get on the sixth quiz?
Thanks.
1 solutions

Answer 204257 by josmiceli(9645) About Me  on 2010-03-15 16:52:52 (Show Source):
You can put this solution on YOUR website!
Let x = lowest score to get on 6th quiz
The average is:
(sum of scores on quizzes)/(number of quizzes) = average grade
For the 1st 5 quizzes, the average is 86
(Sum of scores on 5 quizzes)/5 = 86
Sum of scores on 5 quizzes = 5*86
Sum of scores on 5 quizzes = 430
and, after taking the 6th quiz:
%28430+%2B+x%29%2F6+=+88
Multiply both sides by 6
430+%2B+x+=+6%2A88
430+%2B+x+=+528
x+=+98
Must get at least a 98 to average 88 for 6 quizzes
check:
%28430+%2B+98%29%2F6+=+88
528%2F6+=+88
88+=+88
OK


Exponential-and-logarithmic-functions/281085: what is the sqare root of 64b^48?
1 solutions

Answer 204206 by josmiceli(9645) About Me  on 2010-03-15 14:12:02 (Show Source):
You can put this solution on YOUR website!
As a general rule, I can say that
sqrt%28a%2Ab%5Ec%29+=+sqrt%28a%29%2Ab%5E%28c%2F2%29
Suppose the problem was
4b%5E4
The square root is
2b%5E2 since( 2%2Ab%2Ab)x(2%2Ab%2Ab) = 4b%5E4
Your problem is
sqrt%2864b%5E48%29
sqrt%2864%29+=+8
sqrt%28b%5E48%29+=+b%5E24, so
sqrt%2864b%5E48%29+=+8b%5E24


Travel_Word_Problems/280838: Train A & B are traveling in the same direction on parallel track. Train A is traveling 80 miles per hour and train B is traveling 90 miles per hour. Train A passes station at 3:10 pm If train B passes same station at 3:22 pm what time will train B catch up to train A
1 solutions

Answer 204088 by josmiceli(9645) About Me  on 2010-03-14 21:24:57 (Show Source):
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I have a stopwatch.
I'll start it when the 2nd train, train B, passes the station
Train A passed the station 12 min ago at 3:10
How far did train A get in 12/60 hr? That is his headstart
80%2A%2812%2F60%29+=+16 mi
Now write equations for each train, with time = t for both,
since I'll stop the stopwatch when they meet
d%5BA%5D+=+80t
d%5BB%5D+=+90t
Also note that d%5BA%5D+=+d%5BB%5D+-+16
Substituting:
(1) d%5BB%5D+-+16+=+80t
(2)+d%5BB%5D+=+90t
Substituting again:
90t+-+16+=+80t
10t+=+16
t+=+1.6 hr
B will catch A in 1 hour 36 min, or at 3:22 + 1:36 = 4:58 PM
check:
d%5BA%5D+=+80%2A1.6
d%5BA%5D+=+128
d%5BB%5D+=+90%2A1.6
d%5BB%5D+=+144
144+-+128+=+16
16+=+16
OK


Travel_Word_Problems/280471: On her camping trip Li spent as much time hiking as she did rafting. She traveled 2.5 mph when she was rafting and 3mph when she was hiking. If she went 3 miles more hiking than she did rafting, how far did she hike? Thank you.
1 solutions

Answer 203851 by josmiceli(9645) About Me  on 2010-03-13 20:44:32 (Show Source):
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Let her time for hiking in hours = t
and also her time for rafting = t
Let distance hiking in miles = d%5Bh%5D
Let distance rafting in miles = d%5Br%5D
-----------------------------------
given:
d%5Bh%5D+=+3t
d%5Br%5D+=+2.5t
d%5Bh%5D+=+d%5Br%5D+%2B+3
---------------------
By substitution:
d%5Br%5D+%2B+3+=+3t
d%5Br%5D+=+2.5t
By substitution again:
2.5t+%2B+3+=+3t
.5t+=+3
t+=+6
And, since
d%5Bh%5D+=+3t
d%5Bh%5D+=+3%2A6
d%5Bh%5D+=+18
She hiked 18 miles


Exponential-and-logarithmic-functions/280462: This one looked easy but it's got me confused please help and thank you.
Use the laws of logarithms to express log base2 6 - log base 2 3 + 2 log base 2 sqrt8 as a single logarithm then evaluate. I got this far log base 2^6 - log base2^3 +2 log base 2 sqrt 8 =log base 2 6/3 sqrt8^2??? help
1 solutions

Answer 203850 by josmiceli(9645) About Me  on 2010-03-13 20:34:09 (Show Source):
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log%282%2C6%29+-+log%282%2C3%29+%2B+2%2Alog%282%2Csqrt%288%29%29
The 1st 2 terms are:
log%282%2C6%29+-+log%282%2C3%29+=+log%282%2C6%2F3%29
log%282%2C6%2F3%29+=+log%282%2C2%29
log%282%2C2%29+=+1
So far I have
1+%2B+2%2Alog%282%2Csqrt%288%29%29+=+1+%2B+log%282%2C%28sqrt%288%29%29%5E2%29
1+%2B+log%282%2C%28sqrt%288%29%29%5E2%29+=+1+%2B+log%282%2C8%29
1+%2B+log%282%2C8%29+=+1+%2B+3
1+%2B+3+=+4


Miscellaneous_Word_Problems/280051: From an original group of boys and girls, twenty girls leave. There are then left two boys for each girl. After this, sixty boys leave. There are then two girls for each boy.The number of girls in the original group was:
(A) 81 (B) 72 (C) 68 (D) 60 (E) 50
1 solutions

Answer 203587 by josmiceli(9645) About Me  on 2010-03-12 13:26:52 (Show Source):
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Let g = original number of girls
Let b = original number of boys
given:
Initially, there are:
b+%2B+g in the group
20 girls leave
b+%2B+%28g+-+20%29 in the group
(1) b+=+2%2A%28g+-+20%29
Then 60 boys leave
%28b+-+60%29+%2B+%28g+-+20%29 in the group
(2) g+-+20+=+2%2A%28b+-+60%29
(1) and (2) are 2 equations with 2 unknowns, so
it's solvable
(1) b+=+2%2A%28g+-+20%29
(1) b+=+2g+-+40
(1) 2g+-+b+=+40
(2) g+-+20+=+2%2A%28b+-+60%29
(2) g+-+20+=+2b+-+120
(2) -g+%2B+2b+=+100
Multiply both sides of (1) by 2 and add equations
(1) 4g+-+2b+=+80
(2) -g+%2B+2b+=+100
3g+=+180
g+=+60
The number of girls in the original group was 60
check answer:
(1) b+=+2%2A%28g+-+20%29
b+=+2%2A%2860+-+20%29
b+=+80
(2) g+-+20+=+2%2A%28b+-+60%29
(2) 60+-+20+=+2%2A%2880+-+60%29
40+=+2%2A20
40+=+40
OK


Complex_Numbers/280121: Maple syrup worth $6.00 a gallon and corn syrup worth .80 cents a gallon are used to make a mixture worth $2.36 a gallon. How many gallons of each kind of syrup are needed to make 50 gallons of the mixture?
1 solutions

Answer 203561 by josmiceli(9645) About Me  on 2010-03-12 11:21:39 (Show Source):
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Let m = galloons of maple syrup needed
Let c = gallons of corn syrup needed
given:
m+%2B+c+=+50 gal
600m+%2B+80c+=+236%2A50 (in cents)
By substitution:
600m+%2B+80%2A%2850+-+m%29+=+11800
600m+%2B+4000+-+80m+=+11800
520m+=+7800
m+=+15
and, since
m+%2B+c+=+50
c+=+50+-+15
c+=+35
15 gallons of maple syrup and 35 gallons of corn syrup are needed
check:
600m+%2B+80c+=+236%2A50
600m+%2B+80c+=+11800
600%2A15+%2B+80%2A35+=+11800
9000+%2B+2800+=+11800
11800+=+11800
OK


real-numbers/280060: Two trains, one traveling 10 km/h faster than the other, leave the same station at the same time, one
traveling east and one traveling west. At the end of 6 hours, they are 540 km apart. How far does each train travel?
1 solutions

Answer 203559 by josmiceli(9645) About Me  on 2010-03-12 11:11:19 (Show Source):
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It's the same problem if you think of 1 train
as being stationary, and the other moving at
their added speeds
In 6 hrs:
540+=+r%2A6
r+=+90 km/hr is their added speeds
Their speeds are r%5B1%5D and r%5B2%5D+=+r%5B1%5D+%2B+10
r%5B1%5D+%2B+r%5B1%5D+%2B+10+=+90
2r%5B1%5D+=+80
r%5B1%5D+=+40
r%5B1%5D+%2B+10+=+50
In 6 hrs, 1st train goes
d%5B1%5D+=+40%2A6
d%5B1%5D+=+240 km
and the 2nd train goes
d%5B2%5D+=+50%2A6
d%5B2%5D+=+300 km
check:
240+%2B+300+=+540
OK


Travel_Word_Problems/280067: whta is the speed of a car that travels 60 miles in 20 minutes
1 solutions

Answer 203555 by josmiceli(9645) About Me  on 2010-03-12 11:01:13 (Show Source):
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(60 miles/20 min)x(60 min/1 hr) = 180 mi/hr


Linear_Equations_And_Systems_Word_Problems/280112: The Brooklyn Bridge was built 54 years before the Golden Gate Bridge. In 1983 the Golden Gate Bridge was 23/50 the age of the Brooklyn Bridge. What year was each bridge built?
1 solutions

Answer 203551 by josmiceli(9645) About Me  on 2010-03-12 10:57:17 (Show Source):
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Let y = the year the Brooklyn Bridge was built
Then y+%2B+54 = the year the Golden Gate was built
given:
1983+-+%28y+%2B+54%29+=+%2823%2F50%29%2A%281983+-+y%29
50%2A%281929+-+y%29+=+23%2A%281983+-+y%29
96450+-+50y+=+45609+-+23y
27y+=+96450+-+45609
27y+=+50841
y+=+1883
y+%2B+54+=+1883+%2B+54
y+%2B+54+=+1937
the Brooklyn Bridge was built in 1883
the Golden Gate Bridge was built in 1937
check answer:
1983+-+y+-+54+=+%2823%2F50%29%2A%281983+-+y%29
1983+-+1883+-+54+=+%2823%2F50%29%2A%281983+-+1883%29
100+-+54+=+%2823%2F50%29%2A100
50%2A46+=+2300
2300+=+2300
OK


real-numbers/280061: A car traveling at a rate of 30 km/h left Gander. A second car left Gander 1 hour later. At what rate
must the second car travel to catch up with the first in 3 hours?
1 solutions

Answer 203535 by josmiceli(9645) About Me  on 2010-03-12 10:20:41 (Show Source):
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Start a stopwatch when the 2nd car leaves Gander
When I start the stopwatch, the 1st car has a
30%2A1+=+30 mile head start
When I stop the stopwatch, they both will have
driven for the same time, which is 3 hrs
1st car:
d%5B1%5D+=+30%2A3
d%5B1%5D+=+90 mi
2nd car:
d%5B2%5D+=+d%5B1%5D+%2B+30
d%5B2%5D+=+90+%2B+30
d%5B2%5D+=+120 mi
and
d%5B2%5D+=+r%5B2%5D%2A3
120+=+r%5B2%5D%2A3
r%5B2%5D+=+40
The 2nd car must drive 40 mi/hr to catch the 1st car


Finance/280077: I just need to set this up: I invested X at 10%, and 2X at 12%, for a total interest of 2890. What is X?
1 solutions

Answer 203529 by josmiceli(9645) About Me  on 2010-03-12 10:09:18 (Show Source):


Human-and-algebraic-language/280101: Sherie is goin gto buy a microwave in a city with an 8% sales tax. She has at most $594 to spend. In what price range should she look?
1 solutions

Answer 203525 by josmiceli(9645) About Me  on 2010-03-12 10:06:04 (Show Source):
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Let the price before tax = x
x+%2B+.08x+=+594
1.08x+=+594
x+=+550
The highest price she can afford is $550 before tax


Finance/280100: John put $40 into his investment club every month for a year at a 7% annual interest rate. Interest is calculated once at the end of the year. How much money was in his account at the end of the year?
1 solutions

Answer 203522 by josmiceli(9645) About Me  on 2010-03-12 10:02:08 (Show Source):
You can put this solution on YOUR website!
There are 12 months in a year, so
40%2A12+=+480
.07%2A480+=+33.6
480+%2B+33.6+=+513.6
$513.60 was in the account at the end of the year


Equations/280103: There are 480 dishes that need to be rinsed. John can rinse them in 80 minutes by himself. It will take his friend Bob 120 minutes to rinse these dishes. How long will it take them if they rinse these 480 dishes together?
1 solutions

Answer 203521 by josmiceli(9645) About Me  on 2010-03-12 09:58:25 (Show Source):
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The number 480 does not need to enter the calculations
Just call washing that many dishes 1 job
In words:
(John's rate of working) + (Bob's rate of working) = rate of working together
John's rate = 1 job/80 min
Bob's rate = 1 job/120 min
1%2F80+%2B+1%2F120+=+1%2Ft
Multiply both sides by 120t
1.5t+%2B+t+=+120
2.5t+=+120
t+=+48
It will take them 48 minutes working together


Equations/280104: There is a sales tax of $22 on an item that costs $275 before tax. A second item costs $87.50 before tax. What is the sales tax on the second item?
1 solutions

Answer 203519 by josmiceli(9645) About Me  on 2010-03-12 09:48:58 (Show Source):
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The sales tax will be the same percent rate for both items.
For the 1st item, $22 is what percent of $275?
22%2F275+=+.08 = 8%
For the 2nd item,
.08%2A87.5+=+7
$7 is the sales tax


Linear-systems/280099: train A is traveling at 60 mph and train B at 80 mph. train A passes the station at 810 and train B at 825 at what time will train B catch train A?
1 solutions

Answer 203518 by josmiceli(9645) About Me  on 2010-03-12 09:44:23 (Show Source):
You can put this solution on YOUR website!
Train A has a 15 minute head start over B if you consider
the station as the starting point. In that time, A has gone
.25%2A60+=+15 miles.
Assume I have a stopwatch. I'll start it when B reaches the station
If I stop it when B catches A, both trains will have been moving
for the same length of time, which I'll call t
given:
v%5Ba%5D+=+60 mi/hr
v%5Bb%5D+=+80 mi/hr
d%5Bb%5D+=+d%5Ba%5D+%2B+15 mi
----------------
Now I can write equations for both trains
d%5Ba%5D+=+60t
d%5Ba%5D+%2B+15+=+80t
By substitution,
60t+%2B+15+=+80t
20t+=+15
t+=+3%2F4 hr
Train B will catch train A in 45 min, or at 8:25 + 45 = 9:05
check answer:
d%5Ba%5D+=+60t
d%5Ba%5D+=+60%2A%283%2F4%29
d%5Ba%5D+=+45 mi
and
d%5Ba%5D+%2B+15+=+80t
d%5Ba%5D+%2B+15+=+80%2A%283%2F4%29
d%5Ba%5D+%2B+15+=+60
d%5Ba%5D+=+45 mi
OK


Rational-functions/280098: can you help me with this problem? I don't understand it.
(-5+2i)-(9+3i)
1 solutions

Answer 203515 by josmiceli(9645) About Me  on 2010-03-12 09:18:43 (Show Source):
You can put this solution on YOUR website!
You are asked to subtract 2 complex numbers. You have to subtract the real parts
separately from the imaginary parts. I don't know how far you are with
imaginary numbers, but subtract them like this:
2i+-+3i+=+-i
Now subtract the real parts
-5+-+9+=+-14
The answer is:
-14+-+i


Travel_Word_Problems/280092: The separate sections of rail on a railroad track are 30 ft. long. As the train passes over the point where the sections are joined, there is an audible click. By what fraction must the number of clicks in a minute be multiplied to find the speed of the train in miles per hour?
1 solutions

Answer 203514 by josmiceli(9645) About Me  on 2010-03-12 09:13:20 (Show Source):
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There are 5280 ft in a mile
You will hear 5280%2F30+=+176 clicks/mile
If the train's speed was 1 mile/min, that is 60 miles/hr
So, 176 clicks/min means the train's speed is 60 miles/hr
Therefore, 60%2F176+=+15%2F44 x clicks/min gives the train's
speed in miles/hr


Systems-of-equations/280070: what is the sum of the roots of this equation. ax^2+bx+c=0 im not sure what they mean by this.
1 solutions

Answer 203504 by josmiceli(9645) About Me  on 2010-03-12 08:32:23 (Show Source):
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The roots are the values of x that make
the equation true.
ax%5E2+%2B+bx+%2B+c+=+0
The quadratic formula for the roots is:
x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+
So, the 2 roots are:
x%5B1%5D+=+%28-b+%2B+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+
x%5B2%5D+=+%28-b+-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+
x%5B1%5D+%2B+x%5B2%5D+=+-b%2F%282a%29+-+b%2F%282a%29+
x%5B1%5D+%2B+x%5B2%5D+=+-b%2Fa
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Another way to do it is:
ax%5E2+%2B+bx+%2B+c+=+0
x%5E2+%2B+%28b%2Fa%29%2Ax+%2B+c%2Fa+=+0
Call the roots r%5B1%5D and r%5B2%5D, then
%28x+-+r%5B1%5D%29%2A%28x+-+r%5B2%5D%29+=+0
x%5E2+-+%28r%5B1%5D+%2B+r%5B2%5D%29%2Ax+%2B+r%5B1%5D%2Ar%5B2%5D+=+0
-%28r%5B1%5D+%2B+r%5B2%5D%29+=+b%2Fa
r%5B1%5D+%2B+r%5B2%5D+=+-b%2Fa


Miscellaneous_Word_Problems/280081: A piece of string 15 inches long is cut into four pieces. If each successive piece is half as long as the preceding piece, then the length of the first piece, in inches, is:
(A) 6 (B) 7 (C) 8 (D) 9 (E) 10
1 solutions

Answer 203502 by josmiceli(9645) About Me  on 2010-03-12 08:18:02 (Show Source):
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The lengths are:
L, L%2F2, L%2F4, L%2F8
L+%2B+L%2F2+%2B+L%2F4+%2B+L%2F8+=+15
L%2A%281+%2B+1%2F2+%2B+1%2F4+%2B+1%2F8%29+=+15
L%2A%2815%2F8%29+=+15
L+=+8
L%2F2+=+4
L%2F4+=+2
L%2F8+=+1
8+%2B+4+%2B+2+%2B+1+=+15
(C) 8 in


Miscellaneous_Word_Problems/280080: Sales of cassette tapes of music decreased by 7% per year for 3 years. The percent that best approximates the total percent that sales of cassette tapes of music decreased during this time period is:
(A) 80.4% (B) 79% (C) 34.3% (D) 21% (E) 19.6%
1 solutions

Answer 203501 by josmiceli(9645) About Me  on 2010-03-12 08:08:44 (Show Source):
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Let s = sales 3 years ago
After 1st year:
s+-+.07s+=+.93s
After 2nd year:
.93s+-+.07%2A.93s+
.93s+-+.0651s+=+.865s
After 3rd year:
.865s+-+.07%2A.865s
.865s+-+.061s
.804s
Cassette sales decreased by
s+-+.804s+=+.196s
(E) 19.6%


logarithm/279976: log 28
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Answer 203465 by josmiceli(9645) About Me  on 2010-03-11 22:11:13 (Show Source):


Percentage-and-ratio-word-problems/279975: An instrument store gives a 10% discount to all students off the original cost of an instrument. During a back to school sale an additional 15% is taken off the discounted price. Julie, a student at the local high school, purchases a flute for $306. How much did it originally cost?
1 solutions

Answer 203463 by josmiceli(9645) About Me  on 2010-03-11 22:06:31 (Show Source):
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Let x = original price
After the 1st discount, it cost
x+-+.1x+=+.9x
After the 2nd discount, it costs
.9x+-+.15%2A%28.9x%29+=+.9x+-+.135x
.9x+-+.135x+=+.765x
.765x+=+306
x+=+400
The original cost was $400


Surface-area/279972: how do you find the area when they only give you the diameter?
1 solutions

Answer 203459 by josmiceli(9645) About Me  on 2010-03-11 21:44:17 (Show Source):
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Let r = radius
Le d = diameter
Area = pi%2Ar%5E2
diameter = 2 x radius
radius = diameter/2
Area = pi%2A%28d%2F2%29%5E2


Linear_Equations_And_Systems_Word_Problems/279961: A patch of measuring 6 feet by 6 feet requires 2 ounces of fertilizer. How many pounds should be used on a lawn that measures 30 feet by 75 feet?
1 solutions

Answer 203457 by josmiceli(9645) About Me  on 2010-03-11 21:40:21 (Show Source):
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6%2A6+=+36 ft2
30%2A75+=+2250
2250%2F36+=+62.5
This is the factor to multiply 2 ounces by
2%2A62.5+=+125 ounces needed
To find pounds of fertilizer needed, divide by 16
125%2F16+=+7.8125 pounds
7 pounds and 13 ounces are needed


Linear_Equations_And_Systems_Word_Problems/279960: juan donates 10% of his salary to his church. he earns 3500 per month. he used to earn $3200, an he gave the same dollar amount. what percent of his income does he donate to the church when he earned $3,200?
1 solutions

Answer 203454 by josmiceli(9645) About Me  on 2010-03-11 21:32:40 (Show Source):
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.1%2A3500+=+350
When he earned $3200, he also donated $350
350%2F3200+=+.109
.109%2A100+=+10.9
He donated 10.9% of his income


Mixture_Word_Problems/279858: A 10% salt solution is mixed with an 18% salt solution to obtain a 32 oz 15% solution. How many ounces of each are needed?
1 solutions

Answer 203402 by josmiceli(9645) About Me  on 2010-03-11 18:51:03 (Show Source):
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Let a = ounces of 10% solution needed
Let b = ounces of 18% solution needed
given:
(1) a+%2B+b+=+32 ounces
(2) .1a+%2B+.18b+=+.15%2A32
(2) .1a+%2B+.18b+=+4.8
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Multiply both sides of (2) by 100
(2) 10a+%2B+18b+=+480
Multiply both sides of (1) by 10
and subtract from (2)
(2) 10a+%2B+18b+=+480
(1) -10a+-+10b+=+-320
8b+=+160
b+=+20
and, since
a+%2B+b+=+32
a+%2B+20+=+32
a+=+12
12 ounces of 10% solution and 20 ounces of 18% solution are needed
check:
(2) .1a+%2B+.18b+=+4.8
.1%2A12+%2B+.18%2A20+=+4.8
1.2+%2B+3.6+=+4.8
4.8+=+4.8
OK


Money_Word_Problems/279764: I get paid monthly. I want to know how to figure out how much I earn hourly.
Thank you.
1 solutions

Answer 203351 by josmiceli(9645) About Me  on 2010-03-11 14:35:30 (Show Source):
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There are 4 weeks in a month, and most people work 5 days/week
and 40 hours/day
4%2A5+=+20 days/month of work
Let x = monthly pay in dollars
(x/1 month ) x (1 month/4 weeks) x (1 week/5 days) x (1 day/40 hours) = x/(4 x 5 x 40) = x/800
Hourly, you earn (monthly pay)/800
If you earned $4,000/month, you make
4000%2F800 = $5/hr