Quiz Discussion

A student finds the average of 10 positive integers. Each integer contains two digits. By mistake, the boy interchanges the digits of one number say ba for ab. Due to this, the average becomes 1.8 less than the previous one. What was the difference of the two digits a and b?

• 1] 8
• 2] 6
• 3] 2
• 4] 4

The average age of 24 boys and their teacher is 15 years. When the teacher's age is excluded, the average age decreases by 1 year. The age of the teacher is :

• 1] 38 years
• 2] 39 years
• 3] 40 years
• 4] 41 years

The average monthly salary of 660 workers in a factory is Rs. 380. The average monthly salary of officers is Rs. 2100 and the average monthly salary of the other workers is Rs. 340. Find the number of other workers.

• 1] 645
• 2] 650
• 3] 640
• 4] 642

The average height of 30 boys out of a class of 50 is 160 cm. If the average height of the remaining boys is 165 cm, the average height of the whole class (in cm) is :

• 1] 161
• 2] 162
• 3] 163
• 4] 164

What is the average of the first six (positive) odd number each of which is divisible by 7?

• 1] 42
• 2] 43
• 3] 47
• 4] 49

The average monthly income of P and Q is Rs. 6000; that of Q and R is Rs. 5250; and that P and R is Rs. 5500. What is P’s monthly income?

• 1] Rs. 3500
• 2] Rs. 4500
• 3] Rs. 6250
• 4] Rs. 4800

There are two sections A and B of a class, consisting of 36 and 44 students' respectively. If the average weight of section A is 40kg and that of section B is 35kg, find the average weight of the whole class.

• 1] 30 kg
• 2] 35 kg
• 3] 42.5 kg
• 4] 37.25 kg

10 years ago, the average age of a family of 4 members was 24 years. Two children having been born (with age difference of 2 years), the present average age of the family is again 24 years. Then the present age of the youngest child is:

• 1]

  1 years

• 2]

  2 years

• 3]

  3 years

• 4]

  4 years

A train covers the first 16 km at a speed of 20 km per hour another 20 km at 40 km per hour and the last 10 km at 15 km per hour. Find the average speed for the entire journey.

• 1]

  24 km

• 2]

  26 km

• 3]

  21 km

• 4]

  km

If the arithmetic mean of 0, 5, 4, 3 is a, that of -1, 0, 1, 5, 4, 3 is b and that of 5, 4, 3 is c, then the relation between a, b, and c is

• 1] a = b = c
• 2] a : b : c = 3 : 2 : 4
• 3] 4a = 5b = c
• 4] a + b + c = 12