Vipul spends 30% of his monthly income on rent, 60% of the remaining on groceries, and 40% of the remaining on others. If he saves ₹ 7056 in a month, then how much (in ₹) does he spend on groceries?

Correct — B. Work down the chain, letting "the remaining" mean whatever is left at that moment. Call the monthly income I.

Rent 30% → left 0.7I
Groceries 60% of 0.7I = 0.42I → left 0.28I
Others 40% of 0.28I → left 0.6 × 0.28I = 0.168I

That last figure is the saving:
0.168I = 7056 → I = 42,000
Groceries = 0.42 × 42,000 = 17,640

That is option (b).

Why the others are wrong

• (a)
  18323 — Option (a) 18,323 is about 2.60 times the 7,056 saving. Groceries take 0.42I and the saving is 0.168I, so the two are locked at 5 : 2 whatever the income turns out to be.
• (c)
  22386 — Option (c) 22,386 is about 3.17 times the saving, and it is more than 0.42 × 42,000 — larger than the grocery share can be once 7,056 fixes the income.
• (d)
  15230 — Option (d) 15,230 is about 2.16 times the saving. It would need an income near 36,300, and 16.8% of that is 6,092, not 7,056.

Every percentage after the first is taken on the running remainder, not on the income. That is what "of the remaining" means, and it is the whole difficulty of the item.

As multipliers: rent leaves 0.7, groceries leave 0.4 of that, others leave 0.6 of what is then left. So the saving is 0.7 × 0.4 × 0.6 = 0.168 of income.

Groceries themselves are 0.6 × 0.7 = 0.42 of income. Since 0.42 ÷ 0.168 = 2.5, the grocery bill is always two and a half times the saving — you can answer without ever finding the income.

Key facts

• "Of the remaining" refers to what is left after the previous step, never to the original income.
• Rent at 30% leaves 70%, and groceries at 60% of that come to 42% of income.
• The saving is 0.7 × 0.4 × 0.6 = 16.8% of income, so 7,056 fixes the income at 42,000.
• Groceries and the saving stand in the fixed ratio 42 : 16.8, that is 5 : 2.

Common traps

• Taking 60% and 40% of the original income instead of the running remainder.
• Reporting the income of 42,000 instead of the grocery figure.
• Dividing 7,056 by 0.28 and forgetting the "others" step altogether.

No directly related past PYQ was found.