Mental math worksheets
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Making 100 to add and subtract
Grade 3–4
Add and subtract by pairing numbers that make 100
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In teaching order
Mental math worksheets, easiest first
Each sheet assumes the one above it is comfortable. Start where your child is, not at the top.- Making 100 to add and subtract
Print 37 + 48 + 63 = (37 + 63) + 48 - Round and adjust: adding and subtracting
Print 253 + 298 = 253 + 300 − 2 - Friendly pairs: 25 × 4 and 125 × 8
Print 25 × 36 = 25 × 4 × 9 - Multiplying by 9, 99 and 101
Print 99 × 8 = (100 − 1) × 8 - Split and combine to multiply
Print 37 × 6 + 63 × 6 = (37 + 63) × 6 - Dividing by 5, 25 and 4 in your head
Print 725 ÷ 5 = 725 × 2 ÷ 10 - Mental math strategies
Print 99 × 8 = (100 − 1) × 8
A simple way through mental math
Each strategy rests on one property of the operations: numbers can be added or multiplied in any order, a product can be split into parts, and taking away two numbers is taking away their total. None of this is a trick in the sense of being arbitrary, and each page says why its move works.
Why this order works
The sheets print the working as a textbook does, one equals sign per line. The rewrite — the strategy itself — is printed, and the numbers after it are blanks, so a child practises the method rather than guessing at the answer. In Drill the same questions ask for the answer alone, for when the method is secure.