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

Answer: (b)

Sum of three new numbers = 8 × 8.5 – 7 × 5

= 68 – 35 = 33

∴ Required average = $33/3$ = 11

Answer: (b)

4C = 22 × 4 – 20 × 4 = 88 – 80 = 8

⇒ C = $8/4$ = 2

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: (a)

Total marks of 28 students = 28× 50 = 1400

Total marks of 20 students = 20 × 55 = 1100

∴Total marks of 8 students = 1400 – 1100 = 300

∴ Average = $300/8$ = 37.5

Answer: (b)

Required number = 5 × 140 – 4 × 130

= 700 – 520 = 180

Aliter : Using Rule 25,

Here, x = (140 – 130) = 10, n = 5

Excluded number = Average + x (n – 1)

= 140 + 10 × 4 = 180

Answer: (d)

Weight of the teacher = 42 kg. + ${35 × 400}/1000$kg

= 42 + 14 = 56 kg.

Aliter : Using Rule 24,

Here, x = $400/100$ = 0.4, n = 34

Weight of teacher = Average + x (n + 1)

= 42 + 0.4 (34 + 1)

= 42 + 14 = 56 kg