Average :

1.Rohan purchase 7 toys at the rate of Rs 100 each, 5 toys at the rate of Rs 150 each and 11 toys at the rate of 200 each. Calculate the average cost of one toy.

Solution : Price of 7 toys = 100 × 7 = Rs 700

Price of 5 toys = 150 × 5 = Rs 750

Price of 11 toys = 118 × 15 =Rs 1770

Total number of toys = 7+5+11= 23

Average price of 1 toy = 700+750+1770/23

= 3220/23= Rs140

2. The average marks obtained by 150 students in a certain examination is 55. Find the total marks.

Solution : Total marks = average marks × number of students

= 150 × 55

= 8250

3. The average weight of 44 students of section A of a class is 52 kg. whereas the average weight of 56 students of section B of the same class is 50.5 kg. Find the average weight of all the 100 students of the class.

Solution : Here, A=44, B=56, X=52 and Y=50.5

∴ Average weight of all the 100 students = A × X + B × Y/A + B

= 44 × 52 + 56 × 50.5/44 + 56

= 2288 + 2828/100

= 51.16 kg.

4. If half of the journey is travelled at a speed of 30 km/hr and the next half at a speed of 24 km/hr, find the average speed during the entire journey.

Solution : The average speed

= ( 2XY/X+Y ) = 2 ×30 × 24/30+24

= 1440/54

= 26.66 km/hr

5. A car covers the first 80 kms at a speed of 60 km/hr, another 80 kms at 70 km/hr and last 80kms at 40 km/hr. Find the average speed of the car for the entire journey .

Solution : Average speed = 3XYZ/XY+YZ+ZX

= 3 ×60×70×40/60×70+70×40+40×60

= 504000/4200+2800+2400

= 504000/9400

= 53.61 km/hr