Question

Thirty-six vehicles are parked in a parking lot in a single row. After the first car, there is one scooter. After the second car, there are two scooters. After the third car, there are three scooters and so on. Work out the number of scooters in the second half row.

• A. 15
• B. 17
• C. 12
• D. 10

Hint:

For such problems, consider the sum of a series, where the number of scooters increases after each vehicle. You can sum the numbers for each part of the row.

Answer 1

The Correct Option is A

The total number of vehicles is 36. According to the problem, after each car, the number of scooters increases sequentially (1, 2, 3, 4, etc.). The total number of scooters in the first half is:
- After the first car: 1 scooter
- After the second car: 2 scooters
- After the third car: 3 scooters
- And so on.
The total number of scooters in the first half of the row (18 vehicles) is the sum of the first 9 numbers: \[ 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 = 45 \] The number of scooters in the second half of the row (also 18 vehicles) will be: \[ 10 + 11 + 12 + 13 + 14 + 15 + 16 + 17 + 18 = 15 \] Thus, the number of scooters in the second half of the row is \( \boxed{15} \).