ITPEC FE Subject B October 2024 Question 2

Array Manipulation — filling in blanks for a function that checks product ID's last digit and calculates coupon count.

The function gives 1 coupon per every 3 purchased products, but only if the product ID ends in 3.

Blank A — checking the last digit:
- The last digit of an integer is obtained by prod_id mod 10
- The condition checks prod_id mod 10 = 3
- Options a–c use integer part of (prod_id ÷ 10), which removes the last digit instead of extracting it
- Options d–f compare prod_id to 10 mod 3 = 1, which is meaningless

Blank B — number of coupons:
- "For every purchase of three products → one coupon" means integer division by 3
- integer part of (pur_prod ÷ 3) = floor(pur_prod / 3)
- Example: pur_prod = 7 → floor(7/3) = 2 coupons

Why not others:
- (a–c) integer part of (prod_id ÷ 10) = 3 checks if the tens digit is 3, not the last digit
- (d–f) prod_id = 10 mod 3 compares prod_id to 1, not a valid last-digit check
- (h) + 1 would give an extra coupon (e.g., 3 items → 2 coupons instead of 1)
- (i) pur_prod mod 3 gives the remainder, not the number of complete groups of 3

Key rule: To extract the last digit of an integer, use number mod 10. To count how many complete groups of N fit, use integer part of (number ÷ N).

AI-generated — may contain errors