If three equal distances are covered at different spees of A, B and C km/h, respectively, then average speed during whole journey
= 3ABC/(AB + BC + CA) km/h
? Required average speed
= (3 x 15 x 10 x 5) / (15 x 10 + 10 x 5 + 15 x 5)
= (3 x 15 x 10 x 5)/(150 + 50 + 75)
= (3 x 15 x 10 x 5)/275
= 8.18 km/h
Monthly income of 4 persons = 7350 x 4 = ? 29400
Monthly income of 3 person (excluding the dead person) = 6500 x 3 = ? 19500
? Monthly income of dead person = 29400 - 19500 = ? 9900
Given that total number of students = 150 = ( n1+ n2) and
Mean weight of 150 students = 60 kg.
The mean weight of boys a1= 70 kg and
The mean weight of girls a2 = 55 kg
Let n1 and n2 be the number of boys and girl, respectively.
? n1 + n2 = 150 ...(i)
11 n1 + 11 n2 = 1650 ...(ii)
Average weight = (n1 a1 + n2 a2) / (n1 + n2)
? 60 = (70 n1 + 55n2)/150
? 70 n1 + 55n2 = 9000
? 14n1 + 11n2 =1800 ...(iii)
On subtracting Eq. (ii) from Eq. (iii), we get
3n1 = 150 ? n1 = 50
Hence, required number of boys is 50.
Total weight of 2 men
= 1 x 10 + (42 + 38) = 10 + 80 = 90 kg
? Average weight of 2 men = 90/2 = 45 kg
Total age of 3 woman = 2 X 11 + (32 + 33 + 34)
= 22 + 99 = 121 yr.
? Average age of 3 woman = 121/3 = 401/3 yr
Total age of 4 member = 25 x 4 = 100 yr
Total age of 5 members including the head
= 5 x (25 + 25 x 20/100)
= 5 x 30 = 150 yr
? Age of the head = 150 - 100 = 50 yr
Total temperature of first and fourth days= (4 x 48 - 2 x 34)°C
= (192 - 68)°C= 124°C
Now, according to the question
Temperature of the first day = (9/20) x 124 = 55.8°C
Temperature of fourth day = (11/20) x 124 = 68.2°C
Let the monthly salary of a man = ? N
? The annual salary = ? 12N
According to the question,
Annually spends of a man = 7 x 1694.70 + 5 x 1810.50
= ? 20915.40
? His monthly spends = 20915.40/12 = ? 1742.95
And monthly saving = 3084.60/12 = ? 257.05
? His monthly salary
= 1742.95 + 257.05
= ? 2000
Required average rate of reading
= 2AB / (A + B) = 2 x 60 x 40 / (60 + 40)
= (2 x 60 x 40)/100 = 48 page/h
According to the average speed formula,
P = 1/4, Q =3/5, R = 3/20
x = 8 km/h, y = 6 km/h, z = 10km/h
? Required average speed = 1 / [(P/x) + (Q/y) + (R/z)]
=1 / [(1/32) + (1/10) + (3/200)]
= 1/[(25 + 80 + 12)/800]
= 800/117
= 6.83 km/h
Here, P = 9 km/h, Q = 25 km/h, R = 30 km
x = 3 km/h, y = 5 km/h and z = 10 km/h
? Required average speed
= [P + Q + R] / [(P/x) + (Q/y) + (R/z)] = [9+25 + 30] / [(9/3) + (25/5) + (30/10)]
= 64/(3 + 5 + 3)
= 64/11
= 59/11 km/h
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