WAEC Computer Studies 2021 Theory — Question 4

Model answer

(a) AB1₁₆ = A×16²+B×16¹+1×16⁰ = 10×256+11×16+1 = 2560+176+1 = 2737₁₀. Converting 2737 to octal by repeated division by 8: 2737÷8=342 r1; 342÷8=42 r6; 42÷8=5 r2; 5÷8=0 r5. Reading remainders bottom-up: 5261₈. (b) 1110111.101₂ = (1×2⁶+1×2⁵+1×2⁴+0×2³+1×2²+1×2¹+1×2⁰) + (1×2⁻¹+0×2⁻²+1×2⁻³) = (64+32+16+0+4+2+1) + (0.5+0+0.125) = 119 + 0.625 = 119.625₁₀. (c) 507₈ converts first to decimal: 5×64+0×8+7×1 = 320+0+7 = 327₁₀, then to binary: 327 = 101000111₂.