Simplification and approximation practice that never runs out

Why these two topics come first

SBI Clerk syllabus weightage puts simplification at around 7 to 10 questions in Prelims and approximation at around 3 to 5. Each one should take 20 to 30 seconds once you are fluent. No other topic gives as many marks per minute.

There is a second reason. Every DI question, every percentage problem and every interest calculation ends in arithmetic. Faster simplification makes all of those faster too.

What to memorise before you start

Spend the first week on these alongside practice. Say them aloud, write them out, and test yourself in random order.

Simplification: three worked examples

1. 12.5% of 480 + √729 = ? 12.5% is 1/8, so 480 ÷ 8 = 60. √729 = 27. Answer: 87.
2. 1/4 of 3/5 of 1,240 = ? 3/5 of 1,240 = 744. One quarter of 744 = 186.
3. ? + 156 = 23 × 12. 23 × 12 = 276, so ? = 276 − 156 = 120.

Follow BODMAS strictly: brackets, orders (powers and roots), division and multiplication from left to right, then addition and subtraction from left to right. Most wrong answers in simplification come from doing a subtraction before a multiplication.

Approximation: how rounding works

In approximation, the options are far enough apart that you can round each number to something easy.

1. 39.97% of 799.8 + 14.02 × 11.96 ≈ ? Round to 40% of 800 + 14 × 12 = 320 + 168 = 488.
2. 2,999.8 ÷ 24.9 ≈ ? Round to 3,000 ÷ 25 = 120.
3. √1,023 × 6.02 ≈ ? √1,024 = 32, so 32 × 6 = 192.

A two-week drill plan

After two weeks, keep a 10-minute daily drill going until the exam. Speed fades quickly if you stop.

The errors that cost the most

• Reading "of" wrongly. "Of" means multiply, and it is worked out before division. So 120 ÷ 1/4 of 8 is 120 ÷ 2 = 60, not 120 × 4 × 8.
• Losing a negative sign. In expressions like 84 − 3 × (−6), the answer is 102, not 66.
• Rounding too early in approximation. Round each number once, at the start. Rounding a midway result again stacks the error.
• Choosing the nearest option without checking the gap. If two options are close, your rounding was too rough. Redo one step more precisely.

After each practice session, open the solutions of any wrong answers and label the error with one of these four. Within a week you will know which one is yours.

Why answers are typed here

In topic practice you type the number rather than choose from five options. That removes the temptation to work backwards from options, which feels fast but hides weak arithmetic. In mocks, the questions switch back to options as in the real exam, and then option-checking becomes a useful extra tool rather than a crutch.

Questions people ask