Question

A rhombus sheet, perimeter= meter, diagonal= 10 meter long is to be painted on both sides at rate of Rs. 5 per meter sq. Find the cost of painting.

Answer 1

We know that all the sides of a rhombus are equal.
Let one side be a , thus perimeter = 4a =32
= a = 32/4 = 8m

Now the diagonal divides the rhombus into two triangles of sides 4m, 4m and 10m
Thus area of 1 triangle by herons formula
= 31.225 m²
Total area of Rhombus = 31.225 X 2 = 62.450²

Cost of painting = 5 X 64.450
                           = Rs.312.5
Now it is said to paint both the side, therefore cost to paint the other side = Rs.312.50 
Total Cost = 312.50 + 312.50
                      = Rs.625

Hope that helps !!

Answer 2

I think it may be nearly Rs.625. I found it using the heron's formula, as the diagonal divides it into two.