model 1 basic average questions Section-Wise Topic Notes With Detailed Explanation And Example Questions

Answer: (c)

Sum of 4 new numbers

= 50 ×104 – 100 × 44

= 5200 – 4400 = 800

∴ Average = $800/4$ = 200

Aliter : Using Rule 19,

Here, N = 100, T = 44

n = 4, y = 50 – 44 = 6

∴ Average of new numbers

= T+ $({N/n}+1)$

= 44+ $({100/4}+1) ×6$

= 44 + 26 × 6

= 44 + 156 = 200

Answer: (a)

Value of 13th result

= 25 × 20 – 12 × 15 – 12 × 18

= 500 – 180 – 216 = 104

Answer: (d)

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

Required average

${1.11+0.01+0.101+0.001+0.11}/5$

= ${1.332}/5$ = 0.2664

Answer: (b)

If each number is multiplied by a certain number, then the average is also multiplied by that number.

∴ Required average =7×12 = 84

Answer: (d)

Total expenditure = 120 × 7 = Rs. 840

Total expenditure of 4 boys = 150 × 4 =Rs. 600

Total expenditure of 3 girls = 840 – 600 = Rs. 240

∴ Their average expenditure

= $240/3$ = Rs. 80

Answer: (b)

Total cost price of 20kg of mixed rice

Rs. (12 × 30 + 8 × 40) = Rs.680

∴ Average per kg price = $680/20$ = Rs.34

Aliter : Using Rule 2,

$x_1$ = 12, $A_1$ = 30

$x_2$ = 8, $A_2$ = 40

∴ Average = ${A_1x_1 + A_2x_2}/{x_1+x_2}$

${30×12+40×8}/{12+8}$

${360+320}/20$

= $680/20$

= Rs.34