Leather

First find total area of leather.

Total area which I have is 150 x 180 = 27,000m.

Now find area of all the shapes as per information given.

Area of square = ${ a }^{ 2 }$ = ${ 10 }^{ 2 }$ = 100m.

Area of rectangle = w * l = 25 * 40 = 1000m.

Are of triangle = $\frac { b*h }{ 2 }$ = $\frac { 50*30 }{ 2 }$ = 750m.

Area of circle = $\pi r^{ 2 }$ = $\pi 20^{ 2 }$ = 1256m.

Area of trapezium = $\left( \frac { a+b }{ 2 } \right) *h$ = $\left( \frac { 20+30 }{ 2 } \right) *15$ = 375m.

Area of parallelogram = b * h = 18 * 25 = 450m.

Area of rhombus = $\frac { v*h }{ 2 }$ = $\frac { 26*45 }{ 2 }$ = 585m.

And area of hexagon = $3\frac { \sqrt { 3 } }{ 2 } { a }^{ 2 }$ = $3\frac { \sqrt { 3 } }{ 2 } { 13.5 }^{ 2 }$ = 473.50m.

Total of all shapes = 100 + 1000 + 750 + 1256 + 375 + 450 + 585 + 473.50 = 4989.50m.

We require 5 pieces of each. So 4989.50 * 5 = 24,947.50m of leather we will use.

So left over leather = 2052.50m (27,000-24947.50)

Hence leftover percentage will be 7.60% (2052.50/27,000)