Simple Trick : Sum = (Number of terms) × (Average of first & last) Q. 100 to 200 = ? Q. 400 to 500 = ? Q. 900 to 1000 = ?
Simple Trick : Sum = (Number of terms) × (Average of first & last)
Q. Sum from 100 to 200
- Count how many numbers are there:
- From 100 to 200 = 101 numbers
- Take first + last ÷ 2 = average
- (100 + 200) ÷ 2 = 150
- Multiply:
- 101 × 150 = 15,150
Q. Sum from 400 to 500
- Count how many numbers are there:
- From 400 to 500 = 101 numbers
- Take first + last ÷ 2 = average
- (400 + 500) ÷ 2 = 450
- Multiply:
- 101 × 450 = 45,450
Q. Sum from 900 to 1000
- Count how many numbers are there:
- From 900 to 1000 = 101 numbers
- Take first + last ÷ 2 = average
- (900 + 1000) ÷ 2 = 950
- Multiply:
- 101 × 950 = 95,950