Approximation and Simplification for Bank Prelims: Round, Then Solve

Bank prelims usually open the quant section with a set of calculation questions. In approximation questions the numbers are deliberately awkward, such as 24.98 or 39.97%, and you are expected to round them and pick the nearest option. In simplification questions the numbers are exact and you must follow the order of operations. Both often ask for the value of a question mark somewhere in an equation.

The habit that matters most: glance at the options before calculating. If they are 10 or more apart, rough rounding is enough. If two are close, keep a little more precision.

Most awkward decimals sit just above or below a friendly number. Replace each with that number, then calculate.

The exact value is 450.41, so rounding cost less than half a unit. That is far smaller than the usual gap between options.

Percentages close to 10%, 20%, 25%, 33.33% or 50% can be replaced by the round figure or by the matching fraction. Roots of numbers close to perfect squares round to the root of the square.

When the numbers are exact, rounding is not allowed and the order of operations decides the answer. Brackets come first, then powers and roots, then division and multiplication from left to right, then addition and subtraction from left to right.

The classic trap is doing addition before multiplication, which here would give (18 + 6) × 4 ÷ 3 − 5 = 27. Writing each step on a new line takes a second and prevents it. Full rules and harder cases, including "of" and nested brackets, are in simplification and BODMAS.

A calculation set rewards a steady routine more than clever tricks. Before the exam, make sure the building blocks are automatic: squares up to 30, cubes up to 15, the tables up to 20, and the fraction values of common percentages such as 12.5%, 16.67% and 33.33%. These are what let you round with confidence instead of hesitating.

In the exam, take each question in three passes of a few seconds each:

1. Classify it. Exact numbers mean simplification; awkward decimals mean approximation.
2. Look at the options. Their spacing tells you how roughly you can round.
3. Round once, then calculate, applying the order of operations to the rounded expression.

If an approximation lands almost exactly halfway between two options, your rounding was too coarse. Go back and keep one more digit in the largest term, because that is where most of the error comes from. If an exact simplification gives a value that is not among the options, the usual cause is an order-of-operations slip, so redo it line by line.

• ✘ Rounding a number once to calculate and again to compare, which doubles the error.
• ✘ Rounding the base of a percentage and the percentage itself in opposite directions when options are close.
• ✘ Applying approximation to an exact simplification question.
• ✘ Forgetting that division and multiplication run left to right, not multiplication first.

For estimation inside charts, see approximation for DI. The other prelims staples are number series, quantity comparison and data sufficiency; root shortcuts are in square and cube roots and the Quant cheat code.

How much can I round in approximation questions?

Round each number to the nearest friendly value, usually a whole number, a multiple of 5 or 10, or a perfect square. Bank options are typically spread widely, so small roundings are safe, but check the options first and keep more precision if two are close.

What is the difference between approximation and simplification questions?

Simplification questions use exact numbers and expect an exact answer, so you apply BODMAS carefully. Approximation questions use awkward decimals on purpose, and you are expected to round them to nearby friendly values and choose the closest option.

All problems and solutions on this page are original. No outside facts are relied on; every numeric answer is recomputed by software before publishing.

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