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🧮 Choosing the Best Way to Calculate

Not every sum needs the same trick! Learn to spot when to use a known fact, a quick mental jump, or a pencil — and always pick the smartest, fastest way to find an answer.

3
lessons
~15 min
to learn
🔢 Math
subject
Ages 6–12
level
Start the course →

What you’ll learn

  1. Facts You Just KnowRecall doubles and number bonds to 10 as instant known facts instead of counting.The fastest way to calculate is to already know the answer. Doubles like 5 + 5 = 10 and number bonds like 6 + 4 = 10 can be remembered by heart. Knowing these facts means you never waste time counting the easy ones.
  2. Handy Mental TricksUse counting on, near doubles, and making a ten to add small numbers mentally.When you don't just know a sum, mental tricks help. Count on for small adds (8 + 3 = 9, 10, 11), use a near double for neighbours (6 + 7 = 12 + 1 = 13), and make a ten when a number is close to ten (8 + 5 = 10 + 3 = 13).
  3. Choosing WiselyMatch each calculation to the best method and know when paper beats mental math.Choosing well means looking at a sum before you solve it. Known facts and small jumps belong in your head; near-ten numbers suit making a ten; and big sums with carrying are safest on paper. Picking the right method keeps you fast and correct.

Questions this course answers

Which sum can you answer instantly as a known double?

5 + 5 is a double — the two parts are the same, so it makes 10.

6 and what number make a bond to 10?

6 + 4 = 10, so 4 is the number bond partner for 6.

What is 6 + 7?

6 + 6 = 12, and 7 is one more than 6, so add 1 to get 13.

To add 8 + 5 by making a ten, what do you add to 8 first?

8 needs 2 more to reach 10, so add 2 first, then the leftover 3.

Which sum is best solved by making a ten?

9 is close to 10, so 9 + 1 = 10, then + 5 = 15 — making a ten is quickest here.

Which sum is safest to work out on paper?

46 + 38 has two big numbers and carrying, so writing it down keeps every step safe.

Grounded in trusted sources

  • Khan Academy Kids
  • PBS Kids — early math
  • NRICH — University of Cambridge
  • Britannica Kids

Every Wunder lesson is built from real, reputable sources — never invented.

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