GWD 1-33

[usamiyo]

Q33:
At a certain school, the ratio of the number of second graders to the number of fourth graders is 8 to 5, and the ratio of the number of first graders to the number of second graders is 3 to 4. If the ratio of the number of third graders to the number of fourth graders is 3 to 2, what is the ratio of the number of first graders to the number of third graders?

A. 16 to 15
B. 9 to 5
C. 5 to 16
D. 5 to 4
E. 4 to 5
Ans: E
How to do this one?
How?

[StanleyHuang]

由題目可知
1) Second/Fourth = 8/5
2) First/Second = 3/4
3) Third/Fourth = 3/2
要問First/Third =?
先把 1), 2) 拿來相乘 (Second/Fourth) * (First/Second) = First/Fourth= 24/20 = 6/5
然後由 3) 可得 Fourth/Third = 2/3，再乘上剛才得到的結果可得
First/Third = 12/15 = 4/5