Computation of Whole Numbers
About 7 min · Elementary Mathematics · English
Time worked out from the lesson's 483 words at 150 words a minute, plus a minute for each question.
Computation of whole numbers forms the bedrock of all elementary mathematics in SSC GD. Every calculation you perform in profit-loss, time-distance, mensuration or simplification traces back to these four basic operations: addition, subtraction, multiplication and division. The exam tests your speed and accuracy across mental calculation, column arithmetic and word problems that require choosing the correct operation.
Key ideas
- Whole numbers are the set {0, 1, 2, 3, ...} with no fractions or negative values. Addition and multiplication always stay within whole numbers; subtraction (5 − 7 = −2) and division (5 ÷ 8) may not.
- Place value system organises digits by powers of ten: units, tens, hundreds, thousands, etc. Aligning place values vertically is critical in column addition and subtraction.
- Carrying (addition) and borrowing (subtraction) manage overflow and underflow between place columns. Missing a carry or borrow is a common error.
- Multiplication is repeated addition. Distributive property lets you break large multiplications into manageable parts: 47 × 8 = (40 × 8) + (7 × 8).
- Division produces a quotient and possibly a remainder. For whole numbers: Dividend = Divisor × Quotient + Remainder, where Remainder < Divisor.
Watch out for
- Forgetting to carry or carrying twice: Students write the carry digit in the answer row or forget to add it in the next column. Fix: Mark the carry digit lightly above the next column and cross it off once used.
- Misaligned place values: Writing numbers in a slanted column leads to adding units to tens. Fix: Use graph paper or rule vertical lines to keep digits strictly aligned by place value.
- Borrowing errors in subtraction: Borrowing from a zero requires borrowing from the next non-zero digit, but students stop after one borrow. Fix: Chain the borrows left until you reach a non-zero digit, reducing it by 1 and turning each intermediate zero into 9.
Quick reference
- Addition carry rule: If column sum ≥ 10, write the units digit and carry the tens digit left.
- Subtraction borrow rule: If top digit < bottom digit, borrow 1 from the next left column (reduce it by 1, add 10 to current column).
- Multiplication by powers of 10: Append as many zeros as the power (e.g., 56 × 1000 = 56000).
- Division check formula: Dividend = Divisor × Quotient + Remainder.
- Estimation habit: Round numbers to nearest ten/hundred before computing to predict the answer range.
Check yourself: 3 questions
1. A shopkeeper sold 256 notebooks on Monday, 318 notebooks on Tuesday, and 407 notebooks on Wednesday. How many notebooks did he sell in total during these three days?
2. A factory produces 1248 items per day. If the factory operates for 15 days in a month, how many items will it produce in that month?
3. A container has 8456 litres of water. If 3729 litres are used for irrigation and 2548 litres are used for drinking purposes, how many litres of water remain in the container?
This lesson is cut from the topic's note, not rewritten. Fact-checked on 18 Oct 2026: an AI-assisted check of this note against cited sources; the errors it found were corrected that day. Some errors may remain. The questions are from Shishya's validated question bank.
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