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Times Tables · Lesson 9 of 12

9 Times Table

Multiplying by nine is ten times a number minus the number. In the first ten answers the digits add to nine.

What you will learn

  • Say and write the answers in the 99 times table up to 9×129 \times 12.
  • Use the patterns in the table to check your answers.
  • Use the table to solve simple word problems.

Before you start: you should know multiplication as equal groups. See Multiplication: Equal Groups and Arrays.

The idea

The 99 times table lists 99 multiplied by 1,2,31, 2, 3 and so on up to 1212. Each answer is the number of objects in that many groups of 99.

The whole table

12 by 12 multiplication grid, 9 times table highlightedA grid of products from 1 × 1 to 12 × 12. Row and column headings are the numbers being multiplied, and the 9 times table row and column are shaded.×123456789101112112345678910111222468101214161820222433691215182124273033364481216202428323640444855101520253035404550556066121824303642485460667277142128354249566370778488162432404856647280889699182736455463728190991081010203040506070809010011012011112233445566778899110121132121224364860728496108120132144
The 12 by 12 multiplication grid with the 9 times table shaded. Read along the shaded row for 9 × 1 up to 9 × 12.

Patterns

  • Ten times minus one: 9×79 \times 7 is 70−7=6370 - 7 = 63.
  • The digits of each answer up to 9×109 \times 10 add to nine: 1+8=91 + 8 = 9, 2+7=92 + 7 = 9, 3+6=93 + 6 = 9.
  • The tens digit is one less than the number you multiply by: 9×6=549 \times 6 = 54, and 55 is one less than 66.
  • The answers are 9,18,27,36,45,54,63,72,81,90,99,1089, 18, 27, 36, 45, 54, 63, 72, 81, 90, 99, 108.

Skip counting

Counting in steps of 99 gives the answers one after another.

Number line from 0 to 54Number line from 0 to 54. Jumps: from 0 to 9 (+9), from 9 to 18 (+9), from 18 to 27 (+9), from 27 to 36 (+9), from 36 to 45 (+9), from 45 to 54 (+9).091827364554+9+9+9+9+9+9
Six jumps of 9 from zero land on 9, 18, 27, 36, 45 and 54, the first six answers in the table.

An array

An array shows the same facts as rows and columns.

Array of 4 rows of 94 rows with 9 counters in each row, 36 counters in all.
4 rows of 9. 4 × 9 = 36. Turn it on its side to see 9 × 4.

Worked examples

Example 1: Ten minus one

What is 9×89 \times 8?

  1. 10×8=8010 \times 8 = 80.
  2. Take away one 88: 80−8=7280 - 8 = 72.

Answer: 7272.

Example 2: Digit check

Could 9×69 \times 6 be 5656?

  1. Add the digits of 5656: 5+6=115 + 6 = 11, not 99.

Answer: No. 9×6=549 \times 6 = 54, and 5+4=95 + 4 = 9.

Example 3: Stamps

A sheet has 99 rows of 44 stamps. How many stamps?

  1. 9×49 \times 4: ten fours is 4040.
  2. Take away one four: 3636.

Answer: 3636 stamps.

The digit-sum trick works up to 9×10=909 \times 10 = 90. After that, 9×11=999 \times 11 = 99 adds to 1818, so use ten times minus one instead.

Why it matters

Nines are one less than ten, which is why they are easy to build from the ten times table. The same idea gives quick mental maths for nearly nine, for example 9×25=250−25=2259 \times 25 = 250 - 25 = 225.

Practice

Your turn. Type or choose an answer, then press Check. Getting one wrong is fine, that is what practice is for. You can try as many times as you like.

Question 1 of 8

What is 9×39 \times 3?

Question 2 of 8

What is 9×69 \times 6?

Question 3 of 8

What is 9×89 \times 8?

Question 4 of 8

What is 7×97 \times 9?

Question 5 of 8

What is 9×99 \times 9?

Question 6 of 8

What is 9×129 \times 12?

Question 7 of 8

What is 9×39 \times 3?

Question 8 of 8

Which of these is in the 99 times table?

Choose one answer