Primary 1 Maths: Addition and Subtraction within 20 and 100

Primary 1 Maths: Addition and Subtraction within 20 and 100 — Tutor Lesson Plan

2026-10-27

Tutor lesson-prep guides · Primary maths

No counting on fingers. A ten-frame lets the child see ten, and carrying and borrowing grow out of that picture.

Objectives — the student can add within 20 by making ten, use column addition and subtraction with carrying and borrowing, and check whether an answer is reasonable.

01 Prerequisites (3-minute check)

If any of these fails, fix it before the lesson starts.

Skill	Quick check	Pass mark
Counting to 20	Count from 13 to 20	No gaps
Bonds of 10	Which pairs make 10?	1+9, 2+8, and so on
Comparing	Which is bigger, 17 or 12?	17

02 Lesson flow (40 minutes)

Time	Stage	Tutor does	Student does
0-5 min	Ten-frame	Place 8 counters on a ten-frame	Say how many more fill it
5-14 min	Making ten	8 + 7 as 8 + 2 + 5	Do 9 + 6
14-24 min	Column addition	45 + 28 with carrying	36 + 27
24-32 min	Column subtraction	62 minus 37 with borrowing	51 minus 26
32-37 min	Fix errors	Board the missing carry	Point at the lost ten
37-40 min	Exit check	Three questions marked at once	Finish alone

03 Teaching script (read it out)

Scene 1: See ten first

There are 8 counters in the frame and room for 2 more.
So take 2 from the 7: 10 + 5 = 15. That is faster than counting on.

Student does 9 + 6 as 9 + 1 + 5 = 15.

Scene 2: Column addition: units under units

45 + 28: units 5 + 8 = 13, write 3 and carry 1 into the tens.
Tens: 4 + 2 + 1 = 7, so 73. Always write the carried 1 above the tens.

Student circles the carried 1.

Scene 3: Borrowing: take one ten

62 minus 37: units 2 cannot take 7, so borrow one ten and make 12 − 7 = 5.
The tens become 5, and 5 − 3 = 2, so the answer is 25.

Warn: mark the borrow on the number, not in your head.

04 Question types and worked steps

Type	Example	Steps	Answer
Add within 20	8 + 7	8 + 2 + 5	15
Subtract within 20	16 − 9	16 − 6 − 3	7
Column addition	45 + 28	Carry into the tens	73
Column subtraction	62 − 37	Borrow a ten	25

Sanity check (teach this): A sum is bigger than both numbers and a difference is smaller than the starting number; 62 minus 37 giving 35 means the ten was not repaid.

05 Independent practice (3 questions)

Question	Answer	What to watch
9 + 6	15	Making ten
36 + 27	63	Writing the carry
51 − 26	25	Reducing the tens after borrowing

06 Common mistakes and what to say

Mistake	Student writes	Say this
Counting on fingers	counts one by one	Use the ten-frame and fill to ten.
Carry not written	45 + 28 = 63	Write the 1 above the tens.
Tens not reduced after borrowing	62 − 37 = 35	Borrowing takes one ten away.
Wrong column	45 + 8 written as 45 + 80	The 8 belongs under the units.

07 Homework (paper, section and question numbers)

Primary 1 first-term paper — Section A, questions 1 to 8
Primary 1 second-term paper — Section A, questions 9 to 12

08 Exit check (last 5 minutes)

Question	Answer	Decision
9 + 6	15	All right: move to multiplication
36 + 27	63	One wrong: re-teach carrying
51 − 26	25	Two wrong: repeat the ten-frame

09 Tutor FAQ

Are fingers allowed?

Briefly, yes, but teach making ten at the same time; long-term finger counting slows everything down.

Do we need bought equipment?

No, a ten-frame drawn on paper is enough.

How much practice a day?

Five questions daily, accuracy before speed.

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A TutorZone lesson-prep guide. Written by the TutorZone team; questions and lesson flow are original and are not taken from any school or publisher material.