Tutor:

New! Get regular updates about newly solved problems via algebra.com's RSS system.

---

Recent problems solved by 'robertb'

robertb answered: 4011 problems
Jump to solutions: 0..29 , 30..59 , 60..89 , 90..119 , 120..149 , 150..179 , 180..209 , 210..239 , 240..269 , 270..299 , 300..329 , 330..359 , 360..389 , 390..419 , 420..449 , 450..479 , 480..509 , 510..539 , 540..569 , 570..599 , 600..629 , 630..659 , 660..689 , 690..719 , 720..749 , 750..779 , 780..809 , 810..839 , 840..869 , 870..899 , 900..929 , 930..959 , 960..989 , 990..1019 , 1020..1049 , 1050..1079 , 1080..1109 , 1110..1139 , 1140..1169 , 1170..1199 , 1200..1229 , 1230..1259 , 1260..1289 , 1290..1319 , 1320..1349 , 1350..1379 , 1380..1409 , 1410..1439 , 1440..1469 , 1470..1499 , 1500..1529 , 1530..1559 , 1560..1589 , 1590..1619 , 1620..1649 , 1650..1679 , 1680..1709 , 1710..1739 , 1740..1769 , 1770..1799 , 1800..1829 , 1830..1859 , 1860..1889 , 1890..1919 , 1920..1949 , 1950..1979 , 1980..2009 , 2010..2039 , 2040..2069 , 2070..2099 , 2100..2129 , 2130..2159 , 2160..2189 , 2190..2219 , 2220..2249 , 2250..2279 , 2280..2309 , 2310..2339 , 2340..2369 , 2370..2399 , 2400..2429 , 2430..2459 , 2460..2489 , 2490..2519 , 2520..2549 , 2550..2579 , 2580..2609 , 2610..2639 , 2640..2669 , 2670..2699 , 2700..2729 , 2730..2759 , 2760..2789 , 2790..2819 , 2820..2849 , 2850..2879 , 2880..2909 , 2910..2939 , 2940..2969 , 2970..2999 , 3000..3029 , 3030..3059 , 3060..3089 , 3090..3119 , 3120..3149 , 3150..3179 , 3180..3209 , 3210..3239 , 3240..3269 , 3270..3299 , 3300..3329 , 3330..3359 , 3360..3389 , 3390..3419 , 3420..3449 , 3450..3479 , 3480..3509 , 3510..3539 , 3540..3569 , 3570..3599 , 3600..3629 , 3630..3659 , 3660..3689 , 3690..3719 , 3720..3749 , 3750..3779 , 3780..3809 , 3810..3839 , 3840..3869 , 3870..3899 , 3900..3929 , 3930..3959 , 3960..3989 , 3990..4019, >>Next

Miscellaneous_Word_Problems/474892: In a group of 48 boys, 32 play basketball and 25 play volleyball. How many of the boys play both basketball and volleyball? 1 solutions Answer 325669 by robertb(4012)   on 2011-07-27 04:31:03 (Show Source): You can put this solution on YOUR website! N(basketball AND volleyball) = N(basketball) + N(volleyball) - N(basketball OR volleyball) = 32 + 25 - 48 = 9, so 9 boys play both basketball and volleyball.

Probability-and-statistics/474843: Find the sample size necessary to achieve the following:Margin of error E=0.005, confidence level=99%, when the p is unknown. Again, assume this is an estimation of th population proportoin 1 solutions Answer 325667 by robertb(4012)   on 2011-07-27 04:26:42 (Show Source): You can put this solution on YOUR website! The margin of error is approximately given by , where when the parameter p is unknown. ==> , or n = 66,306.25. So sample size must be at least 66,307.

Divisibility_and_Prime_Numbers/474907: How many integers from -8000 to 8000 are divisible by 4? Please explain how I could approach and solve this, thanks! 1 solutions Answer 325665 by robertb(4012)   on 2011-07-27 04:06:51 (Show Source): You can put this solution on YOUR website! Use the formula for the nth term of an arithmetic series: ==> 8000 = -8000 + (n-1)4 ==> 16000 = 4(n-1) ==> n-1 = 4000 ==> n = 4,001, the number of integers from -8,000 to 8, 000 divisible by 4. (Note that we have let -8,000 be the first term of the arithmetic series, which is actually divisible by 4.)

Probability-and-statistics/474851: Claim: The proportion of people aged 18 to 25 who currently use illicit drugs is equal to 20%. Write the correct symbolic form from H0 and H1 1 solutions Answer 325641 by robertb(4012)   on 2011-07-27 00:55:47 (Show Source): You can put this solution on YOUR website!

Probability-and-statistics/474853: Claim: The majority of college students have credit cards. Write the correct symbolic form for H0 and H1 1 solutions Answer 325635 by robertb(4012)   on 2011-07-27 00:03:17 (Show Source): You can put this solution on YOUR website!

Miscellaneous_Word_Problems/474858: When the number of people who contribute equally to bail a friend out of jail decreases from seven to five, each person must pay and additional $40. What is the cost of the bail? A) $200 B) $280 C) $560 D) $700 E) $880 Please explain how I could approach and solve this, thanks! 1 solutions Answer 325633 by robertb(4012)   on 2011-07-26 23:59:33 (Show Source): You can put this solution on YOUR website! Let x = cost of bail. Then ==> ==> x = 700

Miscellaneous_Word_Problems/473355: Classify the following as an example of a nominal, ordinal, interval, or ratio level of measurement, and state why it represents this level: salaries of the CEOs of seven regional banks Thanks, 1 solutions Answer 325372 by robertb(4012)   on 2011-07-26 02:05:13 (Show Source): You can put this solution on YOUR website! Ratio level. There is an absolute zero for this measurement (Absolute zero = no salary), and all the arithmetical operations (including powers and roots) can be done on these measurements.

Distributive-associative-commutative-properties/473970: Does the commutative property imply the associative property in number systems? 1 solutions Answer 325369 by robertb(4012)   on 2011-07-26 01:37:50 (Show Source): You can put this solution on YOUR website! The two properties deal about two different things. Commutativity talks about how rearranging the ORDER of the factors affects the product, whereas associativity talks about the effects various groupings of the factors have on the product, WITH THE ORDER OF THE FACTORS KEPT FIXED.

Distributive-associative-commutative-properties/474180: (x-2)(x+1)>4 1 solutions Answer 325368 by robertb(4012)   on 2011-07-26 01:29:20 (Show Source): You can put this solution on YOUR website! (x-2)(x+1)>4 <==> <==> <==> (x-3)(x+2) > 0 ==> Solution set is (, -2)U(3, ). (Endpoints not included!)

Triangles/474362: Picture a 45-45-90 triangle. If the short leg equals 5. What is the length of the long leg? 1 solutions Answer 325365 by robertb(4012)   on 2011-07-26 01:23:49 (Show Source): You can put this solution on YOUR website! Multiply the short leg by .

Probability-and-statistics/474387: Past statistics show that a football team scores an average of 3 goals per match. Use a Poisson distribution to find the probability that the team would score exactly 4 goals in a match and at most 2 goals in a match. 1 solutions Answer 325364 by robertb(4012)   on 2011-07-26 01:19:02 (Show Source): You can put this solution on YOUR website! to 3 decimal places. , to 5 decimal places.

Points-lines-and-rays/474389: Determine whether the lines will be perpendicular when graphed. 3x - 2y = 6 2x + 3y = 6 1 solutions Answer 325359 by robertb(4012)   on 2011-07-26 01:04:55 (Show Source): You can put this solution on YOUR website! The slope of the top equation is 3/2, whereas the slope of the bottom line is -2/3. Since the slopes are negative reciprocals of each other, the lines are perpendicular.

Probability-and-statistics/474388: the time taken by the electronic device in a car to respond to a signal from the toll plazza is normally distributed with mean 160 microseconds and standard deviation 30 microseconds. Calculate the probability that the device in the car will respond to the given signal, that is in less than 148 microseconds and within 100 and 180 microseconds. 1 solutions Answer 325358 by robertb(4012)   on 2011-07-26 01:02:49 (Show Source): You can put this solution on YOUR website!

Rational-functions/474382: wha is the inverse of h(x)=x? 1 solutions Answer 325350 by robertb(4012)   on 2011-07-25 23:55:03 (Show Source): You can put this solution on YOUR website! Since there is only one operation present, multiplication (i.e., x = 1*x), the inverse function should "undo" this operation, hence .

Quadratic-relations-and-conic-sections/473981: Show that the equation (x^2)/(5-C) + (y^2)/ (9-C)=1 represents - an ellipse if C is any constant less than 5. - a hyperbola if C is any constant between 5 and 9. - no real locus if C is greater than 9. 1 solutions Answer 325346 by robertb(4012)   on 2011-07-25 23:50:48 (Show Source): You can put this solution on YOUR website! If C < 5, then ==> 5 - C >0, and 9 - C >0, hence the coefficients will be positive, and we get an equation for an ellipse. If 5 < C < 9, then 0 > 5 - C > -4, while 4 > 9 - C > 0. This would give a hyperbola with the y-axis as transverse axis, and the x-axis as conjugate axis. If C > 9, then both 5 - C and 9 - C are negative, and so the left side of the equation is negative while the right side is positive, a contradiction, hence no real locus is formed.

Probability-and-statistics/474287: Determine if this statistical study is descriptive or inferential: A study finds that 51% of registered voters favor candidate X over candidate and why Thank you 1 solutions Answer 325343 by robertb(4012)   on 2011-07-25 23:34:21 (Show Source): You can put this solution on YOUR website! Descriptive, because the figure must have come from a survey or a census.

Rational-functions/474375: what is the inverse of G(x)= x-4? 1 solutions Answer 325342 by robertb(4012)   on 2011-07-25 23:30:33 (Show Source): You can put this solution on YOUR website! Since there is only one operation, subtraction, in the function, its inverse function should "undo" this operation, and so .

Probability-and-statistics/474328: The measure of position called the midquartile of a data set is found using the formula Q1 + Q3/2 Find the midquartile of the given data set. 23 37 47 32 33 41 40 25 31 22 39 42 1 solutions Answer 325341 by robertb(4012)   on 2011-07-25 23:28:59 (Show Source): You can put this solution on YOUR website! 22 23 25 31 32 33 37 39 40 41 42 47 Median = Q2 = 35 Q1 = (25+31)/2 = 28 Q3 = (40 + 41)/2 = 40.5 ==> midquartile = (Q1 + Q3)/2 = (28 + 40.5)/2 = 34.25

Numbers_Word_Problems/473928: the square of a number less that the sum of the number and 8 How to write it in algebraic expression? 1 solutions Answer 325075 by robertb(4012)   on 2011-07-24 23:54:19 (Show Source): You can put this solution on YOUR website!

percentage/473920: write 16/17 as a percent 1 solutions Answer 325066 by robertb(4012)   on 2011-07-24 23:26:52 (Show Source): You can put this solution on YOUR website! % = % = %

Numbers_Word_Problems/473877: in a pond the number of leaves of a lotus plant keep increasing by 1 every day it means 1 leaf on the first day, 2 leaves on the 2nd day, 3 leaves on the third day and so on. find the total number of leaves at the end of 250 days 1 solutions Answer 325063 by robertb(4012)   on 2011-07-24 23:22:21 (Show Source): You can put this solution on YOUR website! + ...+ 250 =.

Permutations/473849: a survey indicates that 30% of students play football, 60% play basketball, and 10% play both. If a student is picked at random, the ODDS that he plays either football or basketball but not both is a. 9 to 1 b. 4 to 1 c. 7 to 3 d. 3 to 2 or e. fifty-fifty can you explain the method of solving it, Does that make sence? 1 solutions Answer 325057 by robertb(4012)   on 2011-07-24 23:14:22 (Show Source): You can put this solution on YOUR website! The problem needs restatement: there is something wrong with the phrase " 30% of students play football, 6% play basketball, and 10% play both"

Matrices-and-determiminant/473872: find all solutions of the system of equations. {x + sqrt (y) = 0 {y^2 - 2x^2 = 3 1 solutions Answer 325055 by robertb(4012)   on 2011-07-24 23:10:07 (Show Source): You can put this solution on YOUR website! Substitute into the bottom equation: , or <==> (y - 3)(y + 1) = 0 ==> y = 3, -1 eliminate y = -1 (Why?) ==> The solution point is thus (, 3)

Probability-and-statistics/473929: Help!!! A class has 17 boys and 10 girls. One student is selected. F is the event of selecting a girl, and K is the event of selecting Kate, one of the girls in the class. Determine P(K | F) and P(F | K). (to three decimal places.) P(K | F)= P(F | K)= 1 solutions Answer 325052 by robertb(4012)   on 2011-07-24 22:58:57 (Show Source): You can put this solution on YOUR website! P(K|F) = P(F|K) =

Probability-and-statistics/473883: A business has several telephone lines. Incoming calls have a Poisson distribution. They come in at the rate of 1 every 75 minutes during daytime hours. What is the probability, over the course of four daytime hours that the business receives: (a) no calls (b) exactly four calls (c) exactly three calls: Show the Poisson formula and the substitution __________________________________________________________________________ (d) at most five calls (e) at least three calls (f) between 3 and 7 calls, inclusive 1 solutions Answer 325050 by robertb(4012)   on 2011-07-24 22:51:44 (Show Source): You can put this solution on YOUR website! I will answer only the first three. I know you'll get the idea for the remaining ones... (a) (b) (c)

Numbers_Word_Problems/473875: find the sum of first 60 multiples of 48 1 solutions Answer 325044 by robertb(4012)   on 2011-07-24 22:28:56 (Show Source): You can put this solution on YOUR website! 48 + 48*2 + 48*3 + 48*4 + ... + 48*60 = 48(1 + 2 + 3 + 4 + ... + 60) =

logarithm/473909: refer to equaliateral if tringle ABC which has perimiter is 39 centermiter . If the midle point of the side conecting midpoints of conecting midle point of side and drawing new tringles is indefinitely. a)write an infinite geometric series to represent the sum of the perimeter of all of the triangle. b) Find the sum of the perimeter of all triangles. 1 solutions Answer 325040 by robertb(4012)   on 2011-07-24 22:21:03 (Show Source): You can put this solution on YOUR website! a) 3*(+...) b) centimeters.

Probability-and-statistics/473913: Help please! The sample space of an experiment is {A, B, C}, where P(A) + P(B) = 0.71, P(B) + P(C) = 0.41. Find P(A), P(B), and P(C). P(A)= P(B)= P(C)= 1 solutions Answer 325038 by robertb(4012)   on 2011-07-24 22:15:07 (Show Source): You can put this solution on YOUR website! We should have P(A) + P(B) + P(C) = 1, so that P(C) = 1 - (P(A) + P(B)) = 1-0.71 = 0.29, P(A) = 1 - (P(B) + P(C)) = 1-0.41 = 0.59. ==> P(B) = 1 - P(A) - P(C) = 1 - 0.59 - 0.29 = 0.12.

Proportions/473921: which is larger 18% of 212 or 1.8% of 2121 1 solutions Answer 325037 by robertb(4012)   on 2011-07-24 22:09:12 (Show Source): You can put this solution on YOUR website! 0.18*212 = 38.16 0.018*2121 = 38.178 Compare.

Probability-and-statistics/473882: Your company has 30 trucks. 11 of them are defective. The inspectors are coming today to inspect, randomly four trucks. You will pass if they find at most one (zero or 1) of them defective. What is your probability of passing? 1 solutions Answer 325036 by robertb(4012)   on 2011-07-24 22:07:31 (Show Source): You can put this solution on YOUR website! , to four decimal places.

Probability-and-statistics/473886: Another problem I need help with In a recent year, the mean number of strokes per hole for a famous golfer was approximately 3.8. Find the variance and standard deviation using the fact that the variance of a Poisson distribution is σ2=μ. How likely is this golfer to play an 18-hole round have more than 72 strokes? The variance is= (round to the nearest tenth as needed) The Standard deviation is_________ Strokes. (round to the nearest then as needed.) The probability of more than 72 strokes in an 18-hole is____(round to the nearest thousandth as needed) Thank you. 1 solutions Answer 325033 by robertb(4012)   on 2011-07-24 21:55:49 (Show Source): You can put this solution on YOUR website! ==> ==> The probability of more than 72 strokes in an 18-hole = .