Rounded to the nearest fifty instead of the nearest hundred: 47 is closer to 50 than to 0, so the student stopped at 3 850. To round to the nearest hundred, examine only the tens digit (4 < 5), which means round down to 3 800.
PRIMARY 4 · MATHEMATICS
Whole Numbers
Top 5 mistakes
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Looked at the ones digit (7 ≥ 5) instead of the tens digit (4 < 5). Rounding to the nearest hundred requires examining the tens digit. Since the tens digit is 4, which is less than 5, round down to 3 800.
Rounded to the nearest thousand instead of the nearest hundred. While 3 847 does round to 4 000 to the nearest thousand (hundreds digit 8 ≥ 5), the question asks for nearest hundred — the answer is 3 800.
This is from a wrong difference progression. T1=5, diff×2 sequence: 3, 6, 12, 24, 48, 96. T7 = 5 + 3 + 6 + 12 + 24 + 48 + 96 = 194 ≈ 197.
Approximate. Compute term by term: T1=5, T2=8 (diff 3), T3=14 (diff 6), T4=26 (diff 12), T5=50 (diff 24), T6=98 (diff 48), T7=194 ≈ 197.
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