18) B
Number of slabs that can be bought with £140 = 140 ÷ 2.80 = 50 slabs
Dimensions of one slab = 70cm x 70cm = 0.7m x 0.7m
Area of 1 slab = 0.7m x 0.7m = 0.49 m²
Area that can be covered with 50 slabs = 50 x 0.49 = 50 x (49/100) = 49/2 = 24.5 m²
We know that the length covered is twice the width. Let the width be W. So length is 2W.
We can form the following equation:
2W x W = 24.5
2W² = 24.5
W² = 12.25
W = 3.5m
So we know the width covered by the slabs = 3.5m
Width of the whole patio= 5m
Width of flower garden = 5 – 3.5 = 1.5m