Math · Stage 5

Multiply numbers just below 100 using complements

When both numbers sit just under 100, you never do long multiplication. Find how far each is from 100, subtract one gap from the other number for the front, multiply the two gaps for the last two digits — a China-fast way to multiply 97 × 96 in your head.

✦ Math📘 Stage 5 · S5⏱ ~10 min🧒 Ages 9–10★ Free to start

I can multiply two numbers just below 100 using the base-100 complement shortcut.

Start the free lesson →⬇ Printable PDF

📖

Kavi's Near-100 Lightning Trick ⚡

"Give me a hard one — 97 × 96," grins Kavi. "I never multiply it the long way. 97 is 3 away from 100, 96 is 4 away. I take 97 − 4 = 93 for the front, then 3 × 4 = 12 for the last two digits. 9,312 — before you even reach for a pencil ⚡."

🎓

What your child will learn

1Step 1 — how far is each number from 100?The whole trick starts with the gap to 100. Here is 96: tap Step → to work out 100 − 96 = 4. That 4 is the gap for 96. In the same way, 97's gap is 100 − 97 = 3. Write the two gaps beside the two numbers — that is all you need.

2Step 2 — subtract the OTHER number's gapFor the front of the answer, take one number and subtract the other number's gap. Tap Step → for 97 − 4 = 93 (4 is 96's gap). Try it the other way too: 96 − 3 = 93 (3 is 97's gap) — the crossing always lands on the same front number.

3Step 3 — multiply the gaps, then joinThe last two digits are just the two gaps multiplied: 3 × 4 = 12. Stick them on the end of the front part. Tap Step → to build 93 | 12 = 9300 + 12.

4Bigger gaps, exactly the same trickNow 92 × 94. Gaps: 8 and 6. Front: 92 − 6 = 86 (or 94 − 8 = 86). Tail: 8 × 6 = 48. Tap Step → to build 86 | 48 = 8600 + 48.

🔍

A peek inside

Multiply 98 × 97 with the near-100 trick.

gaps 2 and 3 → front 98 − 3 = 95, tail 2 × 3 = 6 → write 06

Try this at home: Near-100 trick: 99 × 98 = __ (gaps 1 and 2 → front 99 − 2 = __, tail 1 × 2 = __)

Ready to play and learn?

Start the free interactive lesson, or print the handout for screen-free play.

Start the free lesson →⬇ Download PDF

Part of Math · Stage 5 · S5 on KAVI Academy — a secular, whole-child learning platform for ages 5–12.