model 5 find new average from error Section-Wise Topic Notes With Detailed Explanation And Example Questions

Answer: (d)

Corrected mean = ${80 × 10 – 60 + 50}/10$

= ${800 – 10}/10$ = $790/10$ = 79

Aliter : Using Rule 26,

The correct average will be = m +${\text"(a-b)"}/ \text"n"$.

Here, n = 10, m = 80

a = 50, b = 60

Correct Average = m + ${\text"(a - b)"}/\text"n"$

= 80+$ {(50- 60)}/10$

= 80 – 1 = 79

Answer: (b)

Difference = 62 – 26 = 36

∴ Required average = 47 +$36/20$ = 47 + 1.8 = 48.8

Aliter : Using Rule 26,

The correct average will be = m +${\text"(a-b)"}/ \text"n"$.

Here, n = 20, m = 47

a = 62, b = 26

Correct Average = m + ${\text"(a - b)"}/\text"n"$

= 47 + ${(62 – 26)}/20$

= 47+$36/20$

= 47 + 1.8 = 48.8

Answer: (a)

Difference in observations

= 64 + 28 – 46 – 82 = – 36

∴ Correct average = 124 -$36/18$ = 122

Answer: (c)

Required number = sum of six numbers – sum of five numbers

= 6 × 20 – 15 × 5

= 120 – 75 = 45