1. 3in =5ft, 6in=10ft, 9in=15ft, 12in=20ft, 18in=30ft, 21in=35ft (multiples of 3 for the top row, the bottom row is multiples of 5. when the second column appears 3x2 is 6 and 5x2 is 10, and keep going. whatever number you multiply 3 by is the same number you multiply 5 by.)
a) 30ft
b) Actual is 2.5ft and would be the bottom row. You would divide 5 by 2. Do the same for 3 and it is 1.5in.
2. Scale 2in = 4ft.
The scale dimensions of a room is 14x7
2×x=14 x=7 7×2in=14in. The actual wall would be 7×4=28ft
The scale drawing is 7in. 3.5×2=7in Then 3.5×4=14ft
Final dimensions, 28ft x 14 ft.
3. 2cm = 5m Scale
10cm = 25m. 10cm=2×5. 5m×5=25m
6cm = 15m, 6cm=2×3. 5m×3=15m