12 painters can paint a wall of 180m long in 3 days. How many painters are required to paint 200m long wall in 5 days?
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Solution
Here number of painters are in direct proportion to length the wall and inversely proportional to number of days.
No. of painter
Length of wall (m)
No. of days
12
180
3
x
200
5
12:x
180:200=9:10
3:5
Number of painters α length of the wall 12:x=9:10......... (1) and Number of painters α1numberofdays 12:x= inverse ratio of 3:5 12:x=5:3........(2) from (1) and (2) 12:x= compound ratio of 9:10 and 5:3 12:x=(9:10)×(5:3) 12:x=9×5:10×3 12:x=45:30=3:2 3×x=12×2 x=243=8 Number of painter required =8