How should a challenge item be started?

Write the numbers given first, decide whether to make ten or to compare, then calculate.

How is a how-many-more question done?

Subtract the smaller number from the larger one and keep the unit.

P1 Maths: Addition within 20 (10 Challenge Items)

2026-11-08

Ten challenge items: comparing 9+7 with 8+6, working back to a missing addend, three single digits making 20, 5+5+5+5, deciding whether a sum passes 20, rows of seats and comparing totals.

Reasoning　Write down the numbers given, decide whether to add or subtract, then compare the result with the number asked for.

01　Paper details (check answers afterwards)

Item	Detail
Questions	10
Suggested time	25
Difficulty mix	Foundation 2 · Intermediate 3 · Challenge 3 · Error redo 2
Chapter	Chapter: P1 Maths: Addition within 20
Level	P1 Maths

02　Questions (10 items)

FoundationWhat are 9 + 7 and 8 + 6?
FoundationTwo numbers add up to 18 and one of them is 9. What is the other?
IntermediateWhat is 15 + 4, and what is 1 more than that?
IntermediateWrite one set of three different single-digit numbers that add up to 20.
Intermediate5 + 5 + 5 + 5 = ?
ChallengeIs 7 + 7 + 7 greater than 20? What about 6 + 6 + 6?
Challenge14 + ? = 20. What is the missing number?
ChallengeA hall has two rows of 9 seats. How many seats are there?
Error redoThere are 6 beads; 9 more are added. How many more is that than 12?
Error redoA pupil answers 11 for 3 + 9. What is wrong?

03　Answers and one-line notes

#	Answer	One-line note
1	16 and 14	9 plus 1 makes 10 then add 6 for 16; 8 plus 2 makes 10 then add 4 for 14.
2	9	18 take away 9 is 9, so the two numbers are equal.
3	19 and 20	15 plus 4 is 19, and 19 plus 1 makes exactly 20.
4	9 + 8 + 3 = 20, and other sets also work, for example 9 + 7 + 4.	Make ten first, then use the other two digits to make another ten.
5	20	Four fives add up to 20, which is four times five.
6	7 + 7 + 7 = 21, which is greater than 20; 6 + 6 + 6 = 18, which is not.	Work out each sum first, then compare it with 20.
7	6	20 take away 14 is 6, and 14 plus 6 makes exactly 20.
8	18 seats	9 plus 9 is 18; equal rows are quickest with the doubles fact.
9	There are 15 beads in total, which is 3 more than 12.	Work out 6 plus 9 first, then compare the total with 12.
10	3 plus 9 is 12, not 11.	After making ten from the 9, the remaining 2 must still be 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.