Question:The average weight of `10` oarsmen in a boat is increased by `1.8 kg` when one of the crew, who weights `53` kg is replaced by a new man. Find the weight of the crew, who weights `53 kg` is replaced by a new man. Find the weight of the new man.
Total weight increased `= (1.8 xx 10)` kg `=18` kg. `:.` Weight of the new man `= (53 + 18 )` kg `=71` kg
Question:The average of 11 results is 60. If the average of first six results is 58 and the last six is 63, find the sixth result.
Sixth result `= (6 xx 58 + 6 xx 63 - 11 xx 60)` `= 66`
Question:Distance between two stations A and B is 778 km. Hari Mohan covers the journey from A to B at 84 km per hour and return back to A with a uniform speed of 56 km per hour. Find his average speed during the whole journey.
Required average speed = `(2xy)/(x + y)` km/hr. = `(2 xx 84 xx 56)/(84 xx 56)` km/hr. =`((2 xx 84 xx 56)/140)` km/hr =67.2 km/hr
Question:There are two sections A and B of a class, considering of 36 and 44 students respectively. If the average weight of section A is 40 kg and that of section B is 35 kg, find the average weight of the whole class.
Total weight of (36 + 44) students =(36 x 40 +44 x 35) kg =2980 kg. `:.` Average weight of the whole class =`2980/80` kg =37.25 kg.
Question:The average weight of A, B, C is 45 kg. If the average weight of A and B be 40 kg and that of B and C be 43 kg, find the weight of the whole class.
A + B + C = (45 x 3) kg =135 kg. A + B = (40 x 2) =80 kg & B + C =(43 x 2) = 86 kg. `:.` B = (A + B) + (B + C) - (A + B + C) = (86 + 80 - 135) kg = 31 kg.