# Consider the First 10 Positive Integers. If We Multiply Each Number by −1 and Then Add 1 to Each Number, the Variance of the Numbers So Obtained is (A) 8.25 (B) 6.5 (C) 3.87 (D) 2.87 - Mathematics

MCQ

Consider the first 10 positive integers. If we multiply each number by −1 and then add 1 to each number, the variance of the numbers so obtained is

•  8.25

• 6.5

• 3.87

• 2.87

#### Solution

The first 10 positive integers are 1, 2, 3, 4, 5, 6, 7, 8, 9, 10.

Multiplying each number by −1, we get

−1, −2, −3, −4, −5, −6, −7, −8, −9, −10

Adding 1 to each of these numbers, we get

0, −1, −2, −3, −4, −5, −6, −7, −8, −9

Now,

$\sum_{} x_i = 0 + \left( - 1 \right) + \left( - 2 \right) + \left( - 3 \right) + \left( - 4 \right) + \left( - 5 \right) + \left( - 6 \right) + \left( - 7 \right) + \left( - 8 \right) + \left( - 9 \right) = - 45$

$\sum_{} x_i^2 = 0 + 1 + 4 + 9 + 16 + 25 + 36 + 49 + 64 + 81 = 285$

∴ Variance of the obtained numbers

$= \frac{\sum_{} x_i^2}{10} - \left( \frac{\sum_{} x_i}{10} \right)^2$

$= \frac{285}{10} - \left( \frac{- 45}{10} \right)^2$

$= 28 . 5 - 20 . 25$

$= 8 . 25$

Concept: Statistics - Statistics Concept
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#### APPEARS IN

RD Sharma Class 11 Mathematics Textbook
Chapter 32 Statistics
Q 18 | Page 51