model 4 find nth average from 1st & last number Section-Wise Topic Notes With Detailed Explanation And Example Questions

Answer: (a)

Using Rule 1,

Average of two or more numbers/quantities is called the mean of these numbers, which is given by

$\text"Average(A)" = \text"Sum of observation / quantities"/\text"No of observation / quantities"$

∴ S = A × n

Sixth number

= 6 × 32 + 6 × 37 – 11 × 35

= 192 + 222 – 385 = 29

Answer: (c)

Using Rule 1,

a + b + c = 45 and

b + c + d = 48

⇒ b + c = 48 – 19 = 29

∴ a + b + c = 45

⇒ a = 45 – 29 = 16

Answer: (b)

Using Rule 1,

Average of two or more numbers/quantities is called the mean of these numbers, which is given by

$\text"Average(A)" = \text"Sumof observation / quantities"/\text"No of observation / quantities"$

∴ S = A × n

Fourth number

= (4×4+4×4 – 3×7)

= (16 +16-21) = 11

Answer: (a)

Sum of remaining 10 numbers

= 12 × 15 – 2 × 14

= 180 – 28 = 152

∴ Required average =$152/10$

= $76/5$ = 15$1/5$

Answer: (d)

Using Rule 1,

Sum of remaining two numbers

= 6 × 3.95 – 2 × 3.4 – 2 × 3.85

= 23.7 – 6.8 – 7.7 = 9.2

∴ Required average = ${9.2}/2$= 4.6

Answer: (a)

Using Rule 1,

Average of two or more numbers/quantities is called the mean of these numbers, which is given by

$\text"Average(A)" = \text"Sum of observation / quantities"/\text"No of observation / quantities"$

∴ S = A × n

Last number = Sum of 20 numbers

– sum of first 12 numbers – sum of next 7 numbers

= 20 × 12 – 11 × 12 – 7 × 10

= 240 – 132 – 70 = 38