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Maths · Grade 4 · Set B
Rows, factors and primes
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B
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Goal: 15 min
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Remember: A factor pair is two numbers that multiply to make a number. A prime has only two factors, 1 and itself. A multiple is on the number's times table.

Rows and partners

1
21 plants are in 3 equal rows. How many plants are in each row? 3 × = 21
2
40 cookies are on a tray in 5 equal rows. How many cookies are in each row? 5 × = 40
3
Which tray shows 18 cookies?
A
B
C
4
7 × = 28
5
Is 27 a multiple of 6?
YesNo
6
36 tiles are in 4 rows of 9. Which number is also a factor of 36?
72128

All the factors

7
Is 27 prime, composite or neither?
CompositePrimeNeither
8
Join each number to its factor pairs.
  1. 18
  2. 218
  3. 39
  4. 411
  • A1 × 18, 2 × 9, 3 × 6
  • B1 × 11
  • C1 × 9, 3 × 3
  • D1 × 8, 2 × 4
9
24 tiles make rectangles 1 by 24, 2 by 12, 3 by 8 and 4 by 6. How many factors does 24 have?
10
The tiles make a rectangle with 3 rows of 6. Circle every factor of 18.
246912
11
The table shows the only rectangle 13 tiles can make. So 13 is a prime number.
TrueFalse
12
Put the numbers in order from the fewest factors to the most factors.
  • 11
  • 18
  • 25
  • 10
13
Write every factor of 16 in order. Tell how you know you found them all.
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Answer key · Set B
Rows, factors and primes
17 Count one row: 7 plants. 3 × 7 = 21, so 7 is the partner of 3.
28 Count one row: 8 cookies. 5 × 8 = 40.
3C Tray A has 4 × 5 = 20, tray B has 3 × 5 = 15 and tray C has 3 × 6 = 18.
44 7 rows of 4 tiles make 28.
5No Count by 6s: 6, 12, 18, 24, 30. You jump over 27, so it is not a multiple of 6.
612 3 × 12 = 36, so 12 is a factor. 72 is a multiple of 36, and 8 does not go into 36.
7Composite 3 × 9 = 27, so 27 has more than two factors. It is composite.
81-D, 2-A, 3-C, 4-B
98 The factors are 1, 24, 2, 12, 3, 8, 4 and 6. Each pair gives two factors, so there are 8.
102, 6, 9 2 × 9 = 18, 3 × 6 = 18, so 2, 6 and 9 are factors. 4 and 12 do not go into 18.
11True 13 has only two factors, 1 and 13. A number like that is prime.
121, 4, 2, 3 11 has 2 factors (1, 11), 25 has 3 (1, 5, 25), 10 has 4 (1, 2, 5, 10) and 18 has 6 (1, 2, 3, 6, 9, 18).
13Your own words: a grown-up reads it.
Mark each answer, count the right ones and write the score on the sheet.