Is a missing addend found by adding or subtracting?

By subtracting: total minus the known number, then check by adding both numbers back.

Which pair should be added first in a three-number sum?

The pair that makes ten, such as 4 and 6, then add the third number.

P1 Maths: Addition within 20 (10 Advanced Items)

2026-11-08

Ten advanced items: 6+7, 9+9, 8+8 and 8+9 with make-ten and doubles, the sums 5+6+8 and 4+7+6, carrying in 14+6, and missing addends found by subtraction.

Missing addend　Subtract the known number from the total, then check by adding the two numbers again.

01　Paper details (check answers afterwards)

Item	Detail
Questions	10
Suggested time	25
Difficulty mix	Foundation 3 · Intermediate 3 · Challenge 3 · Error redo 1
Chapter	Chapter: P1 Maths: Addition within 20
Level	P1 Maths

02　Questions (10 items)

Foundation6 + 7 = ?
Foundation9 + 9 = ?
FoundationWhat are 8 + 8 and 8 + 9?
Intermediate5 + 6 + 8 = ?
Intermediate14 + 6 = ?
Intermediate12 + ? = 20. What is the missing number?
Challenge9 + ? = 16. What is the missing number?
ChallengeA bus has 7 people on board and 8 more get on. How many people are on the bus?
Challenge4 + 7 + 6 = ?
Error redoA pupil works out 8 + 9 as 8 + 10 = 18. What is wrong, and what is the correct answer?

03　Answers and one-line notes

#	Answer	One-line note
1	13	6 plus 4 makes 10, then add 3 to get 13.
2	18	9 plus 1 makes 10, then add 8 to get 18.
3	16 and 17	8 plus 8 is 16, and 8 plus 9 is one more, which is 17.
4	19	5 plus 6 is 11, then add 8 to get 19.
5	20	The ones digits 4 and 6 make 10, so 1 is carried and the tens digit goes from 1 to 2, giving 20.
6	8	20 take away 12 is 8, so subtraction finds the missing addend.
7	7	9 plus 7 is 16, and 16 take away 9 also gives 7.
8	15 people	7 plus 8 makes 15, and the unit is people.
9	17	First 4 plus 6 makes 10, then add 7 to get 17.
10	The correct answer is 17: the 9 was treated as 10, so 1 must be taken back.	After making ten, remember to take back the extra one that was added.

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.

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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.