Q.1 Average marks in a class of 30 students are found to be 45. On checking two mistakes were found. After correction if one student got 45 marks more & another student got 15 marks less, then the corrected average marks are :

A) 47

B) 44

C) 46

D) 45

Ans. C

Total marks of 300 students before correction = 30*45 = 1350

& total marks of 30 students after correction = 1350+45-15

= 1380

Therefore, corrected average marks 1380/30 = 46

Q.2 Average salary of entire staff in an office is Rs. 120 per month. The average salary of officers is Rs. 460 & that of non-officers is Rs. 110. If the number of officers is 15, then find the number of non-officers in the office ?

A) 500

B) 550

C) 510

D) 445

Ans. C

Let number of non-officers be x

110x + 460 * 15 = 120(15+x)

120 – 110x = 460*15 – 120*15

= 15(460-120)

10x = 15*340

X= 15*34

= 510

Q.3 A cricketer has completed 10 innings & his average is 21.5 runs. How many runs must he make in his next Innings so as to raise his average to 24 ?

A) 25

B) 45

C) 30

D) 49

Ans. D

10 (24 – 21.5) + 24

= 25 + 24 = 49

Q.4 Rahina did a Mathematic test. In this test Each correct answer scored 8 marks & each incorrect answer reduced score by 4 marks. The test contained 30 Questions & after completing it ,Rahina had a score of Zero. How many Questions did she answer correctly ?

A) 8

B) 10

C) 15

D) 12

Ans. B

8x – 4y = 0

X + y = 30

On solving,

We get x = 10

Q.5 A tree is 8.4 m tall, another is half its height and the third one is its quarter. What is the average height of the trees?

A) 4.55 m

B) 4.6 m

C) 4.9 m

D) 4.8 m

Ans. C

Height of the first tree = 8.4 m tall

Height of the second tree = ½ 8.4 = 4.2 m

Height of the third tree = ¼ 8.4 = 2.1 m

Total height = 8.4 + 4.2 + 2.1 = 14.7

Average height = = 4.9 m