ITPEC FE Subject A October 2025 Question 2
Source exam: ITPEC FE Subject A October 2025Topic: Basic Theory & Math
ITPEC FE Subject A October 2025 — Question 2 of 60
Bit Shifting for Multiplication — compute 9 × n using shifts and addition.
9 × n = 8n + n = (n << 3) + n
- •Left shift by k bits = multiply by
2^k - •
n << 3=8n - •
8n + n=9n
Why not others:
- (a) n << 2 + n = 4n + n = 5n
- (b) n << 2 − n = 4n − n = 3n
- (d) n << 3 − n = 8n − n = 7n
Key rule: To multiply by K, decompose K into powers of 2 and combine with add/subtract. E.g., 9 = 8 + 1, 7 = 8 − 1, 5 = 4 + 1.
AI-generated — may contain errors
The original exam layout is preserved in the image so diagrams, formulas, tables, and code remain accurate.
This question comes from an official ITPEC past paper. ITPEC Practice is an independent study tool and is not affiliated with ITPEC. See the official FE past-paper collection or Report an issue.