The figure, not drawn to scale, is made up of two identical right-angled triangles, a small square and a big square. The lengths of the 2 squares are whole numbers. The perimeter of the shaded region is 64 cm, and the total area of the two unshaded squares is 410 m
2. Find the total area of the two shaded right-angled triangles.
Perimeter of the shaded area = 64 cm
2 lengths of big square + 2 lengths of small square + 2 x 6 = 64
2 lengths of big square + 2 lengths of small square + 12 = 64
2 lengths of big square + 2 lengths of small square = 64 - 12
2 x (1 length of big square + 1 length of small square) = 52
1 length of big square + 1 length of small square = 52 ÷ 2 = 26
Use guess and check.
Total length of the smaller unshaded square and bigger unshaded square must be 26 m.
Length of the smaller unshaded square |
Area of the smaller unshaded square |
Length of the bigger unshaded square |
Area of the bigger unshaded square |
Total unshaded squares |
6 |
6 x 6 = 36 |
20 |
20 x 20 = 400 |
36 +400 = 436 (X) |
8 |
8 x 8 = 64 |
18 |
18 x 18 = 324 |
64 + 324 = 388 (X) |
7 |
7 x 7 = 49 |
19 |
19 x 19 = 361 |
49 + 361 = 410 (✓) |
Length of the smaller unshaded square = 7 m
Length of the bigger unshaded square = 19 m
Total areas of the shaded right-angled triangles
= 19 x 7
= 133 m
2 Answer(s): 133 m
2