P5 Maths: Mean (Basics) (Paper 4 (error Clinic))

P5 Maths: Mean (Basics) (Paper 4 (error clinic))

2026-11-15

Tutor Prep Guide · Using the mean as total over count in all three directions, rebuilding totals and missing items, changes after adding or removing data, combining groups, weighted means and diagnosing common slips

P5 Maths: Mean (Basics) (Paper 4 (error clinic))

Paper 4 (error clinic): ten mean questions on computing the mean, rebuilding totals and combining groups, with answers and one-line notes.

Direct answers　Level: P5 maths; format: computing the mean, rebuilding totals and missing items, adding or removing data, combining groups and weighted means.

01　Paper details (check answers afterwards)

Item	Detail
Questions	10
Suggested time	20
Difficulty mix	Foundation 3 · Intermediate 3 · Challenge 3 · Error redo 1
Chapter	Chapter: P5 Maths: Mean (Basics)
Level	P5

02　Questions (10 items)

FoundationFind the mean of 6, 9 and 12.
FoundationFive numbers total 45; find the mean.
FoundationFind the mean of 10, 10, 20 and 20.
IntermediateSeven numbers have a mean of 8; find their total.
IntermediateFour numbers average 13 and three of them are 12, 15 and 10; find the fourth.
IntermediateThree scores 70, 80 and 90 average 80; what fourth score gives a mean of 82?
ChallengeSix students average 40 kg; after one leaves the remaining five average 38 kg; find the weight of the one who left.
ChallengeA set has a mean of 15; after adding 45 the mean becomes 20; how many numbers were there?
ChallengeClass A has 25 students averaging 68 and class B has 15 averaging 76; find the combined mean.
Error redoError clinic: eight numbers total 96 and a student answered 96 as the mean. Find the correct mean.

03　Answers and one-line notes

#	Answer	One-line note
1	9	The sum 27 divided by 3 gives 9.
2	9	45 divided by 5 gives 9.
3	15	The sum 60 divided by 4 gives 15.
4	56	8 times 7 gives 56.
5	15	The total 52 minus 37 leaves 15.
6	88 marks	The four-test total must be 328 and 240 is already scored, so 88 more is needed.
7	50 kg	The totals are 240 and 190, so the difference is 50 kg.
8	5	With n numbers, 15n plus 45 equals 20 times n plus 1, so n equals 5.
9	71 marks	The totals are 1700 and 1140, and 2840 divided by 40 gives 71.
10	12	The total must be divided by the count, so 96 over 8 gives 12.

04　What to do after marking

After marking, redo only the wrong items and write down which step went wrong (formula, unit, or misread number).
Repeat the same item two days later; move to the next paper only when both attempts are correct.
Parents only need the answer and note columns; there is no need to explain every item.

Check the answers, and for any wrong item write down the total and the count first, then compute the mean again.Tutor Registration →

Questions and answers are written originally by the TutorZone team and are not taken from any school, publisher or examination authority paper. Every value is checked by computer.