Saves time in long calculations
Helps check whether an answer is reasonable
Used heavily in Banking, SSC, NRA CET, Railways, CAT, MAT, CSAT, etc.
1. Rounding to nearest integer
If decimal part ≥ 0.5 → Round up
Example: 3.8 → 4
If decimal part < 0.5 → Round down
Example: 7.2 → 7
2. Rounding to nearest tens
Look at the last digit:
Example: 67 → 70 (since 7 ≥ 5)
⭐ 5 Solved Examples of Approximation (With Explanation)
Round each number to nearest integer:
Now add:
38 + 12 = 50
Round values to nearest convenient number:
Multiply:
50 × 20 = 1000
Round numerator and denominator:
Now divide:
500 ÷ 30 ≈ 16.67
7.2 ≈ 7
Now square:
7² = 49
Nearest perfect square to 63 = 64
√64 = 8
📝Explanation:
Since decimal is 0.4 (<0.5), we round up only if ≥0.5. But 49.4 is close to 49.
However, correct rule:
● 49.4 < 49.5 → Round down → 49
Correct answer = 49.
📝 Description:
7.6 ≈ 8
8.3 ≈ 8
8 + 8 = 16
Correct answer: 16
📝 Description:
9.8 ≈ 10
2.3 ≈ 2
10 × 2 = 20
📝 Description:
128 ≈ 130
4.9 ≈ 5
130 ÷ 5 = 26
Correct answer = 26
📝 Description:
Nearest square to 50 = 49
√49 = 7
📝 Description:
199 ≈ 200
5.1 ≈ 5
200 × 5 = 1000
📝 Description:
48% ≈ 50% = 1/2
98 ÷ 2 ≈ 49 → Approx = 49 → Closest = 45
📝 Description:
78.9 ≈ 79
19.3 ≈ 19
79 – 19 = 60
📝 Description:
6.4 ≈ 6
7.6 ≈ 8
6 × 8 = 48
📝 Description:
0.48 ≈ 0.5
0.51 ≈ 0.5
0.5 × 0.5 = 0.25
📝 Description:
389 ≈ 400
98 ≈ 100
400 ÷ 100 = 4
📝 Description:
27.9% ≈ 30%
30% of 300 = 0.3×300 = 90 (closest: 80)
📝 Description:
9.99 ≈ 10
10² = 100
📝 Description:
499 ≈ 500
298 ≈ 300
199 ≈ 200
500 + 300 + 200 = 1000
📝 Description:
7.9 ≈ 8
125×8 = 1000
Closest to options = 1000
📝 Description:
63.2 ≈ 64
7.9 ≈ 8
64 ÷ 8 = 8
📝 Description:
18.7 ≈ 19
5.8 ≈ 6
19×6 = 114 → approx = 110
📝 Description: Approx values → 2 × 8 = 16
📝 Description:
29.8 ≈ 30
30² = 900
📝 Description:
198 ≈ 200
49.9 ≈ 50
24.7 ≈ 25
Approx = (200×50)/25
= 10000 / 25
= 400
Closest = 350? No.
Actual approx = 400
Correct = 400
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