Flashcards in GMAT advanced Maths Deck (5):
GMATAdvanced GMAT Math QuestionsVersion 2
Quantitative –Fractions and Ratios21. EAnswers1. The current ratio of boys to girls at a certain school is 2to 5. If 12 additional boys were added to the school, the new ratio of boys to girls would be 4 to 9. How many boys currently attend the school?
Quantitative –Work3(A) 1 (B) 5(C) 7(D) 25(E) 351. If 7 workers can build 7 cars in 7 days, then how many days would it take 5 workers to build 5 cars? (A) 28 (B) 30(C) 32(D) 36(E) 403.
If 7 workers are building 7 cars in 7 days then
7 workers are building 7/7= 1 car per day
Therefore each worker is building 1/7 car per day
Then 5 workers are building 5/7 cars per day
Then to build 5 cars
Rate*time = work
T=5*7/5= 7 days
Bea can paint a house three times faster than Alice can paint a house. If, working together, it takes Alice and Bea 24 hours to paint a house, then how many hours will it take Bea to paint a house alone?2.
Alice and Bea 24 hours to paint a house: means that in 1 hr they will complete 1/24th of the work.
Bea can paint a house three times faster than Alice can paint a house: Means that if alice takes t time to complete a work Bea will take (1/3) t to complete same work.
Alice - takes t time to complete 1 work - in 1 hr it will do - 1/t work
Bea- takes (1/3)t time to complete the same work- in 1 hr it will do- 1/(t/3) work= 3/t work
1/t+ 3/t = 1/24
Solving this we get t=96. So bea will take 1/3 *96 = 32 hrs to do the work.
If 6 workers can build 4 cars in 2 days, then how many days would it take 8 workers to build 6 cars?
6 workers can build 4 cars in 2 days.
1 worker can build 4 cars in 2*6 = 12 days
1 worker can build 1 car in 12/4 = 3 days
1 worker can build 6 cars in 3*6 = 18 days
8 workers can build 6 cars in 18/8 = 9/4 days
The correct answer is (B).