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NCERT Solutions Ganita Prakash Chapter 10 Credits and debits — Figure it Out

Book page 260 Updated on2026-09-05

Q1.
Suppose you start with ₹0 in your bank account, and then you have credits of ₹30, ₹40, and ₹50, and debits of ₹40, ₹50, and ₹60. What is your bank account balance now?
Answer

Credits are positive, debits are negative. Add them all.

Credits: 30 + 40 + 50 = + 120
Debits: 40 + 50 + 60 = – 150
Balance = (+ 120) + (– 150) = – ₹30

Answer: the balance is – ₹30 — the account is ₹30 in debt.

Why negative: more money went out than came in. 150 – 120 = 30, and since the debits are larger, the answer carries the debit's minus sign.
Q2.
Suppose you start with ₹0 in your bank account, and then you have debits of ₹1, 2, 4, 8, 16, 32, 64, and 128, and then a single credit of ₹256. What is your bank account balance now?
Answer
Total of the debits: 1 + 2 + 4 + 8 + 16 + 32 + 64 + 128
= 3 + 4 + 8 + 16 + 32 + 64 + 128
= 7 + 8 + 16 + 32 + 64 + 128 = 15 + 16 + 32 + 64 + 128
= 31 + 32 + 64 + 128 = 63 + 64 + 128 = 127 + 128 = 255
Balance = (– 255) + (+ 256) = + ₹1

Answer: the balance is ₹1.

Did you know? The debits are the powers of 2, and their running total is always one less than the next power of 2: 1 + 2 + 4 + … + 128 = 256 – 1 = 255. That is why a single credit of ₹256 leaves exactly ₹1.
Q3.
Why is it generally better to try and maintain a positive balance in your bank account? What are circumstances under which it may be worthwhile to temporarily have a negative balance?
Answer

Why a positive balance is better:

  • A negative balance means you owe money to the bank, and the bank charges interest or a fee on it — so you end up paying extra.
  • Money kept in the account may even earn interest instead of costing it.
  • A positive balance is a safety net for an emergency — a hospital bill, a broken cycle, school fees.
  • Banks trust customers who keep a positive balance, so getting a loan later becomes easier.

When a temporary negative balance can still be worthwhile:

  • To buy stock or a machine for your business that will earn back more than it cost — exactly what happened on page 259, where the ₹150 purchase brought ₹200 the next day.
  • In an emergency — medicines, an operation, or urgent travel — where waiting is not an option.
  • For something that will save money later, such as paying school fees on time to avoid a late-fee penalty.
The rule of thumb: going below zero is sensible only when the money borrowed brings back more than the interest and fees you pay for it, and only for a short time.
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