(1) A construction project consisting of 12 semi-detached houses can be completed in 18 months by 54 men. Find the number of men required to complete another similar project consisting of 35 semi detached houses which must be built in 12 months.
(2) The size if Singapore on a map with a scale of 1:50000 is reflected as 2730.8 cm2 and the coastline is reflected as 386cm. The size of Singapore when drawn on another map of a different scale is 10923.2 cm2. Find the length of coastline as reflected on this second map.
Answer:
(1)
12 houses-----18 months------- 54men
1 house------1.5 month-------- 54men (use 18 divide by 12 to get 1.5)
36 houses------54 months------- 54 men (1.5 x 36 will get 54, this is working with 54men)
So if I want to complete the house in 12 months,
36 house----54 months----- 54men
36 house----1 month---- 54*54 = 2916 men
36 house----12 months---- 2916/12 = 243 men
Thus, 243 men are required to complete another similar project consisting of 35 semi detached houses which must be built in 12 months.
(2)
The difference in ratio between the two maps is
sqrt( 10923.2 / 2730.8 ) = 2
so, coastline of second map / 386 = 2 (not area, so dun need to square it)
coastline of second map = 2 * 386 = 772
