Hi All,

Ratio questions on the GMAT can be dealt with in a variety of different ways. This question is ultimately about the arithmetic involved, so as long as you understand the 'relationship' among the 3 ingredients, the math involved will be pretty easy.

We're given a ratio of cement, sand and gravel as 1:3:5 by weight. This means that for every 1 kg of cement, we'll mix in 3 kg of sand and 5kg of gravel....

1+3+5 = 9 kg of concrete

We're asked for the greatest number of kilograms of this mixture that can be made with 5 kilograms of cement...

From the prior work, we know that 1 kg of cement will get us 9 km of concrete. Since we're dealing with 5kg of cement, we'll end up with (5)(9) = 45 kg of concrete.

Final Answer:

GMAT assassins aren't born, they're made,
Rich
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I worked in this way, can you confirm that is right please?

since we have the ratio of cement, sand and grevel = 1:3:5, which makes a total of 9.
If I add 5 kg to cement I have to multiply also 3*5=15 and 5*5=25. If I sum these vaules I get 45.

Right?

Hi Pepo,

Yes, your idea is correct - I'm just going to 'edit' your language a bit...

You're STARTING with 5kg of cement. Since the ratio is 1:3:5, that means you're multiplying the "1" by "5" to get 5kg... so you have to multiply the other two numbers in the ratio by 5 (the "3" and the "5"). Doing so gives you...

5 kg cement + 15 kg sand + 25 kg gravel = 45 kg concrete

GMAT assassins aren't born, they're made,
Rich
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