Standard Mathematics Primary 3 Multiplication and Division

Ahmad wants to calculate 6 × 48 mentally. Which decomposition gives the fastest correct answer?

A (6 × 50) − (6 × 2) = 300 − 12 = 288
B (6 × 40) + (6 × 8) = 240 + 48 = 288
C (6 × 48) = 6 × 4 × 8 = 192
D (6 × 50) − 2 = 300 − 2 = 298
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Worked Solution

Step 1: Notice 48 is close to the round number 50. Step 2: Rewrite 48 as (50 − 2). Step 3: Apply the distributive property: 6 × (50 − 2) = (6 × 50) − (6 × 2). Step 4: Compute each part: 6 × 50 = 300; 6 × 2 = 12. Step 5: Subtract: 300 − 12 = 288. Step 6: The most efficient option is the round-then-adjust strategy. Answer: (6 × 50) − (6 × 2) = 300 − 12 = 288

Correct answer: (6 × 50) − (6 × 2) = 300 − 12 = 288

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