Approximation Tricks for Bank Exams

How to round

• Decimals → nearest whole number: 24.97 → 25, 59.06 → 59, 399.96 → 400.
• Square roots → nearest perfect square: √780 ≈ 28 (28² = 784), √1442 ≈ 38 (38² = 1444), √290 ≈ 17 (17² = 289).
• Percentages → nearest friendly value: 19.98% → 20%, 24.9% → 25% (= 1/4).
• Divisions → make the divisor round: 2950.01 ÷ 59.06 ≈ 2950 ÷ 59 = 50.

Strategy

• Round first, then apply BODMAS — never calculate with the raw decimals.
• If two options are close, round one term up and another down so the errors cancel.
• For “? ” on the right side (e.g. 400 × ? = 2000), solve for ? last: ? = 2000 ÷ 400 = 5.
• A quick sense check: the answer must be the same size as your rough estimate. Wildly different? Recheck the rounding, not the arithmetic.

Squares 1–30

1²

1

2²

4

3²

9

4²

16

5²

25

6²

36

7²

49

8²

64

9²

81

10²

100

11²

121

12²

144

13²

169

14²

196

15²

225

16²

256

17²

289

18²

324

19²

361

20²

400

21²

441

22²

484

23²

529

24²

576

25²

625

26²

676

27²

729

28²

784

29²

841

30²

900

Cubes 1–20

1³

1

2³

8

3³

27

4³

64

5³

125

6³

216

7³

343

8³

512

9³

729

10³

1000

11³

1331

12³

1728

13³

2197

14³

2744

15³

3375

16³

4096

17³

4913

18³

5832

19³

6859

20³

8000

Fraction → percentage

1/2

50%

1/3

33.33%

1/4

25%

1/5

20%

1/6

16.67%

1/7

14.29%

1/8

12.5%

1/9

11.11%

1/10

10%

1/11

9.09%

1/12

8.33%

1/13

7.69%

1/14

7.14%

1/15

6.67%

1/16

6.25%

1/17

5.88%

1/18

5.56%

1/19

5.26%

1/20

5%