SOLUTION: Alexa and Zack are solving the following problem: The number of miles on Car A is 50 miles more than the number of miles on Car B, and the number of miles on Car B is 30 miles more

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Question 987464: Alexa and Zack are solving the following problem: The number of miles on Car A is 50 miles more than the number of miles on Car B, and the number of miles on Car B is 30 miles more than the number of miles on Car C. All the cars travel 50 miles in 1 hour. After 1 hour, twice the number of miles Car A is 70 miles less than 3 times the number of miles on Car C. How many miles were there on Car B initially? Alexa assumes there are m miles on Car B. Zack assumes there are m miles on Car C. Will Zack's answer be the same as Alexa's answer? Explain.
Found 3 solutions by ankor@dixie-net.com, Silver_surfer, greenestamps:
Answer by ankor@dixie-net.com(22740)   (Show Source): You can put this solution on YOUR website!
Alexa and Zack are solving the following problem:
The number of miles on Car A is 50 miles more than the number of miles on Car B,
a = b+50
and the number of miles on Car B is 30 miles more than the number of miles on Car C.
b = c+30
or
c = b-30
All the cars travel 50 miles in 1 hour.
All travel at 50 mph
After 1 hour, twice the number of miles Car A is 70 miles less than 3 times the number of miles on Car C.
2(a+50) = 3(c+50) - 70
2a + 100 = 3c + 150 - 70
2a = 3c + 150 - 70 - 100
2a = 3c - 20
Replace a with (b+50), replace c with (b-30)
2(b+50) = 3(b-30) - 20
2b + 100 = 3b - 90 - 20
2b + 100 = 3b - 110
2b = 3b - 110 - 100
2b = 3b - 210
210 = 3b - 2b
b = 210 mi car B initially
then
a = 210 + 50
a = 260 car A initially
and
c = 210 - 30
c = 180 mi Car C initially

Alexa assumes there are m miles on Car B.\
Zack assumes there are m miles on Car C.
Will Zack's answer be the same as Alexa's No

Answer by Silver_surfer(1)   (Show Source): You can put this solution on YOUR website!
Alexa and Zack are solving the following problem: The number of miles on Car A is 50 miles more than the number of miles on Car B, and the number of miles on Car B is 30 miles more Car C. All the cars travel 50 miles in 1 hour. After 1 hour, twice the number of miles on Car A is 70 miles less than 3 times the number of miles on Car C.
How many miles were there on Car B initially?
================================================================================
set Car A = a
set Car B = b
set Car C = c

a = 50 + b
b = 30 + c
2a = 3c - 70 rewritten c = (2a+70)/3

b = 30 + c

b = 30 + (2a+70)/3 substitute c

b = 30 + [2(50 + b) + 70 )]/3 substitute a

3b = 90 + 100 + 2b + 70 multiply both sides by 3

b = 260 simplify

Car B had 260 miles initially.
Car A had 310 miles
Car C had 230 miles

================================================================================

Alex assumes Car B has m miles.
Zack assumes Car C has m miles.

Will Zack’s answer be the same as Alex’s? No.

There can be one correct answer and since Car B and Car C had different miles, Zack is incorrect.

Answer by greenestamps(13195)   (Show Source): You can put this solution on YOUR website!


Ignore the solution from the other tutor. It does not use all of the given information to set up the problem correctly; and it does not interpret the question that is asked correctly.

The two students are solving the same problem in different ways; as long as their work is correct, they should (and will) get the same answer.

The given information is that car A has 50 more miles than car B and car B has 30 more miles than car C.

Alexa's solution....

Let m = miles on car B
Then m+50 = miles on car A
and m-30 = miles on car C

After 1 hour at 50mph, the numbers of miles on each car are
A: m+100
B: m+50
C: m+20

At that time, twice the number of miles on car A is 70 less than 3 times the number of miles on car C:

2(m+100)=3(m+20)-70
2m+200=3m-10
m=210

Alexa's answer: the number of miles on car B initially was m=210.

Zack's solution....

Let m = miles on car C
Then m+30 = miles on car B
and m+80 = miles on car A

After 1 hour at 50mph, the numbers of miles on each car are
A: m+130
B: m+80
C: m+50

At that time, twice the number of miles on car A is 70 less than 3 times the number of miles on car C:

2(m+130)=3(m+50)-70
2m+260=3m+80
m=180

Zack's answer: the number of miles on car B initially was m+30=210.

ANSWER: Zack's answer will be the same as Alexa's.


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