练习题 · 英文原题 · SEL-MA-TST-31
Chairs are set out in rows in a school hall. The first row has 14 chairs. Each row after that has 3 more chairs than the row in front of it.
How many chairs are in row 9?
查看答案与解析(英文)
答案: C
Answer: C (38)
- From row 1 to row 9 there are 8 steps, and each step adds 3 chairs.
- Extra chairs: 8 × 3 = 24.
- Row 9: 14 + 24 = 38 chairs.
- Check by listing: 14, 17, 20, 23, 26, 29, 32, 35, 38.
Why the other options are wrong
- A (27): This is 9 × 3, which leaves out the 14 chairs that the first row starts with.
- B (35): This is the number of chairs in row 8; it adds 3 only seven times.
- D (41): This adds 3 nine times, but there are only 8 steps from row 1 to row 9.
- E (126): This multiplies 14 by 9, as if every row had 14 chairs.
