Standard Mathematics Primary 4 Factors and Multiples

Ravi's teacher writes this challenge on the board: "Find a number that is both a factor of 84 and a multiple of 7." Which of the following numbers satisfies BOTH conditions?

A 12
B 21
C 35
D 49
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Worked Solution

Step 1: Understand the two conditions. Condition A: the number must be a factor of 84 (84 ÷ number = whole number, no remainder). Condition B: the number must be a multiple of 7 (number = 7 × whole number). Step 2: List factors of 84. 1, 2, 3, 4, 6, 7, 12, 14, 21, 28, 42, 84 Step 3: From the factors of 84, identify which are also multiples of 7. 7 = 7 × 1 ✓ 14 = 7 × 2 ✓ 21 = 7 × 3 ✓ 28 = 7 × 4 ✓ 42 = 7 × 6 ✓ Step 4: Check which of the answer options appears in the list above. 21 is in the list → 21 is a factor of 84 AND a multiple of 7. The answer is 21.

Correct answer: 21

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