Let me walk you through both ratios step by step.
Key Idea: For each ratio, figure out how many 'batches' you can make before running out of either powder. The powder that runs out first is the limiting factor.Ratio A (Column A): 3g of X to
2g of Y
Each batch uses
3g of X +
2g of Y =
5g of alloy per batch.
How many batches can X support?
90 /
3 =
30 batches
How many batches can Y support?
80 /
2 =
40 batches
X runs out first (
30 <
40), so
X is the limiting factor. We can only make
30 batches.
Total alloy from Ratio A = 30 x 5 = 150 grams (Row 2)Sanity check: This uses
90g of X (all of it) and
60g of Y (within the
80g supply). Works perfectly.
Ratio B (Column B): 11g of X to
10g of Y
Each batch uses
11g of X +
10g of Y =
21g of alloy per batch.
How many batches can X support?
90 /
11 =
8.18 → only
8 full batches
How many batches can Y support?
80 /
10 =
8 batches
Both powders allow exactly
8 batches (Y is the binding constraint since we can't do a partial batch of X either).
Total alloy from Ratio B = 8 x 21 = 168 grams (Row 5)Sanity check: This uses
88g of X (within
90g) and
80g of Y (all of it). Works perfectly.
Answer: Row 2 for Column A (150 grams) and Row 5 for Column B (168 grams)The core technique here is simple: divide each supply by the amount needed per batch, take the smaller whole number (that's your limiting factor), then multiply by the total grams per batch. This 'limiting reagent' concept shows up frequently in GMAT ratio problems.