model 6 find average of excluded number Section-Wise Topic Notes With Detailed Explanation And Example Questions

Answer: (d)

Suppose the initial expenditure per day = Rs. x

⇒ $x/35$ - ${x+42}/42$ = 1

⇒ ${6x-5x-210}/210 = 1$

⇒ x = 210 + 210 = Rs. 420

Answer: (a)

Let the new observation be x. Then,

${x+6×45.5}/7$= 47

⇒ x + 273 = 47 × 7 = 329

⇒ x = 329 – 273 = 56

Aliter : Using Rule 24,

Here, x = (47 – 45.5) = 1.5, n = 6

New observation = Average + x (n + 1)

= 45.5 + 1.5 (6 + 1)

= 45.5 + 10.5 = 56

Answer: (d)

Total sum of five numbers = 27 × 5 = 135

Total sum of four numbers = 25 × 4 = 100

∴ Required number = 135 – 100 = 35

Answer: (b)

Total weight 12 parcels = 12 × 1.8 = 21.6 kg.

New average of 13 parcels = 1.8 – 0.05 = 1.75 kg.

Total weight of 13 parcels = 13 × 1.75 = 22.75 kg.

∴ Weight of new parcel = 22.75 – 21.6 = 1.15 kg.

Aliter : Using Rule 18,

( If in the group of N persons, a new person comes at the place of a person of 'T’ years, so that average age,

increases by 't’ years

Then, the age of the new person = T + N.t. )

Here, T = 1.8, N= (12 + 1) = 13, t = $50/1000$ = .05

Weight of new parcel = T – Nt

= 1.8 – 13 × 0.05

= 1.8 – 0.65 = 1.15 kg

Answer: (b)

4C = 22 × 4 – 20 × 4 = 88 – 80 = 8

⇒ C = $8/4$ = 2