Integers · Add integers · 4.2

Add same sign.

When both numbers have the same sign, there are no zero pairs: add their sizes and keep the shared sign. −3 + (−4) = −7.

01 / THE IDEA

See it work.

Zero pairs

A +1 and a −1 cancel.

-3 + -4

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Watch the method

Add same sign

−3 + (−4): add 3 and 4, keep negative → −7.

1 / 2
−3+−4-3 + -4
1

Same sign — add the sizes

Both are negative, so add their sizes: 3 + 4.

3+4=73 + 4 = 7
2

Keep the sign

Both negative → the answer is negative.

−3+(−4)=−7-3 + (-4) = -7
02 / YOUR TURN

Practice until it feels automatic.

Your turn

Work it out.

Type a whole number — negatives allowed, e.g. -7.

streak 0
best 0
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— / WHY IT WORKS

The idea underneath.

No cancelling

Same-colour counters never cancel, so pile them together: the total keeps the sign.

Why it works

Two debts add to a bigger debt.

03 / WORKED EXAMPLES

From easy to tricky.

EX 1easy

Add 2 + 11

1

Same sign — add the sizes

Both are positive, so add their sizes: 2 + 11. 2 + 11 = 13

2

Keep the sign

Both positive → the answer is positive. 2 + 11 = 13

EX 2medium

Add -3 + -4

1

Same sign — add the sizes

Both are negative, so add their sizes: 3 + 4. 3 + 4 = 7

2

Keep the sign

Both negative → the answer is negative. -3 + (-4) = -7

EX 3hard

Add -12 + -12

1

Same sign — add the sizes

Both are negative, so add their sizes: 12 + 12. 12 + 12 = 24

2

Keep the sign

Both negative → the answer is negative. -12 + (-12) = -24

04 / COMMON TRAPS

Where students slip.

Trap

Subtracting when the signs match.

Fix

Same signs add, not subtract.

Trap

Dropping the negative sign.

Fix

Keep the shared sign on the total.

05 / QUIZ

Test yourself.

The Test

12 problems across three tiers. Auto-graded on submit. Hints and a full walkthrough on every question. Your work is saved on this device — sign in to keep it across devices.

0/12Answered
How to answerType just the value. Formatting won't trip you up — we ignore spaces, capital letters, commas, and subscript style, so t₁ = 5, d = 3 and t1=5,d=3 both count. For a list of numbers, separate them with commas (e.g. 3, 10, 17).
Core

Core (4)

C1

Add 2 + 11

Need a hint?
  • Add the two sizes.
  • Keep the sign they share.
C2

Add -6 + -5

Need a hint?
  • Add the two sizes.
  • Keep the sign they share.
C3

Add -10 + -8

Need a hint?
  • Add the two sizes.
  • Keep the sign they share.
C4

Add 11 + 3

Need a hint?
  • Add the two sizes.
  • Keep the sign they share.
Apply

Apply (4)

A1

Add -3 + -4

Need a hint?
  • Add the two sizes.
  • Keep the sign they share.
A2

Add -11 + -4

Need a hint?
  • Add the two sizes.
  • Keep the sign they share.
A3

Add 4 + 7

Need a hint?
  • Add the two sizes.
  • Keep the sign they share.
A4

Add -8 + -8

Need a hint?
  • Add the two sizes.
  • Keep the sign they share.
Extension

Extension (4)

E1

Add -12 + -12

Need a hint?
  • Add the two sizes.
  • Keep the sign they share.
E2

Add 2 + 9

Need a hint?
  • Add the two sizes.
  • Keep the sign they share.
E3

Add -12 + -9

Need a hint?
  • Add the two sizes.
  • Keep the sign they share.
E4

Add 3 + 12

Need a hint?
  • Add the two sizes.
  • Keep the sign they share.