Question

Find the sum of all odd numbers between 10 and 200.

Answer 1

● Arithmetic Progression ●

Odd numbers between 10 and 200 = 11, 13, 15, ..... 199

First term = a = 11

Common difference = d = 13 - 11 = 2

Last term = l = 199

Now, n = ?

l = a + (n - 1)d

=> 199 = 11 + (n - 1)2

=> 199 = 11 + 2n - 2

=> 2n = 199 - 9

=> n = 190/2

=> n = 95

So, there are 95 odd numbers between 10 and 200.

Sum of the numbers = n/2 × (a + l)

= 95/2 × (11 + 199)

= 95/2 × 210

= 95 × 105

= 9975

Answer 2

Answer:

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