The average of 5 numbers is 7. The sum of four of the numbers is 24. Find the fifth number.

(a)  

What is the average time of the two fastest boys?

(a)  

Mr Sim sold an average of 25 curry puffs per day from Monday to Friday. He sold a total of 47 curry puffs on Monday and Tuesday. What was the average number of curry puffs he sold from Wednesday to Friday?

(a)  

The average of three numbers is 12. The sum of the two if the numbers is twice that of the third number. What is the third number?

(a)  

Alan, Bob, Charlie and Donald have an average mass of 58 kg. The combined mass of Alan and Bob is 28 kg more than the combined mass of Charlie and Donald. Alan’s mass is 49 kg, what is Bob’s mass?

(a)  

The average of two numbers X and Y is 28. The ratio of X to Y is 5 : 2. What is the difference between the two numbers?

(a)  

Mr Loo recorded the test scores for a class of 20 pupils and found the average score to be 80 marks. Upon checking, he realised he had incorrectly recorded a score of 80 marks as 40 marks. What should the correct class average score be?

(a)  

A 3-cabin train on the Express Line has an average number of 190 passengers per cabin. The first cabin has 50 more passengers than the third cabin. The second cabin has twice as many passengers as the third cabin. How many passengers are there in the second cabin?

(a)  

The average number of sweets in 5 boxes was 47. When Sally took one box of sweets away, the average number of sweets in the remaining boxes became 49. How many sweets did Sally take?

(a)  

David, Eugene and Felix collected some stamps. The average number of stamps David and Eugene collected was 73, the average number of stamps Eugene and Felix collected was 91 and the average number of stamps David and Felix collected was 67. How many stamps did they collect?

(a)  

The average height of a group of children was 135.6 cm. When Mr Wong measured and recorded the height of these children, he wrongly recorded one child’s height as 173 cm when it should have been 137 cm. As a result, Mr Wong re-calculated the average height to be 133.2 cm. How many children were there in the group?

(a)  

The average age of a group of children is 11 years old. When Joanne, who is 7 years old, joined the children, the average age of the group becomes 10 years old. How many children are there in the group after Joanne joined in?

(a)