If s and t are positive integers and s/t = 39.12, then which one of th

Could you please explain following step: 978*3/25*3=X/75[/m]

I don't understand why you multiplied everything by 3.

Thanks

i could not understand the solution,any alternate method ?

Flixus16 he multiplied the fraction set forth above by 3 to get 75 as multiple of 25. The reasoning behind is that you need 25 or a multiple of it. Hence, 25*3= 75.

[quote="Bunuel"]If s and t are positive integers and s/t = 39.12, then which one of the following could t equal?

(A) 8
(B) 13
(C) 15
(D) 60
(E) 75



Bunuel, could you please explain why this doesn't align with the very similar (almost exact) question that has s/t=64.12? The solution for that question shows that simplifying 12/100 to 3/25 results in the solution having to be a multiple of 3. In that problem, there was only 1 answer with a multiple of 3.

In this situation, it is the same simplification of 12/100 into 3/25. However for this problem that thought process does not work the same as there are several options for multiples of 3. Why is there a different approach here if the problem is exactly the same?

s/t = 39.12 = 39 12/100 = 39 3/25

Hence, answer choice must be a multiple of 25. Only choice (E) satisfies this condition.

Answer: E

Solution

Given

• s and t are positive integers
• s/t = 39.12

To find

• Find one of the possible value of t

Approach and Working out

• s=39 t + 0.12 t
• S and t are integer.

o So, 0.12 t must also be an integer.
o 0.12 t= 12/100 t = 3/25t
o For 3/25 t to be an integer, t must be divisible by 25.

Hence, option E is the correct answer.

Correct Answer: Option E

We can create the equation:

s/t = 39 + 12/100

s/t = 39 + 3/25

Since s/t = Q + r/t, we see that t must be a multiple of 25, so t could be 75.

Answer: E

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