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5th grade · Math · Unit 7 of 15

Mental Math Tricks

Facts to 81 and clever shortcuts

What your child practices

Recalling multiplication and division facts to 9 × 9, and mental strategies such as adding zeros, halving and doubling, and breaking a number into friendly parts.

New York State Learning Standards learning standard: NY-5.NBT.5; NY-5.NBT.2 · mental multiplication strategies and patterns when multiplying by powers of 10

How we explain it

Children can open this short lesson before they practice.

  1. Use facts you know to find ones you do not: 6 × 8 is double 3 × 8.
  2. Break a number apart: 7 × 12 = 7 × 10 + 7 × 2.
  3. Doubling and halving can make a product easier.

Example: Use a trick: 9 × 7 = ? 9 × 7 is 10 × 7 minus one 7. 70 − 7 = 63. Answer: 63

Mental Math Tricks in New York

In the New York State Learning Standards, this is unit 7 of 15 in 5th grade Math, after Patterns & Equations and before Parallel Lines and Quadrilaterals.

Gradelings describes a child's practice on this unit as Beginning, Approaching, Meeting or Exceeding (Four practice steps). That reflects practice, not a report-card mark: the teacher decides the mark.

Source: New York State Education Department (NYSED)

Sample questions

A taste of this unit. In the app, questions change every time and get easier or harder to match your child.

  1. Question 1

    6 × 7 = ?

    • 42
    • 36
    • 48

  2. Question 2

    4 × 25 = ?

    • 75
    • 125
    • 100

  3. Question 3

    Which fact helps you solve 54 ÷ 6?

    • 6 × 8 = 48
    • 6 × 9 = 54
    • 9 × 9 = 81

  4. Question 4

    7 × 200 = ?

    • 14,000
    • 1,400
    • 140

  5. Question 5

    9 × 8 = 72. What is 9 × 80?

    • 7,200
    • 72
    • 720

  6. Question 6

    15 × 6 = ?

    • 75
    • 90
    • 80

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