PSLE The perimeter of figure BCDEF is (5
r + 21) cm. The perimeter of square BCDE is 16 cm.
- Find the perimeter of triangle BEF in terms of r.
- The perimeter of figure BCDEF is 61 cm. What is the value of r? Give your answer in cm.
(a)
Length of the square
= 16 ÷ 4
= 4 cm
Total lengths of BC, CD and DE
= 3 x 4
= 12 cm
Perimeter of triangle BEF
= 5
r + 21 - 4 - 4
= (5
r + 13) cm
(b)
5
r + 21 = 61
5
r = 61 - 21
5
r = 40
r = 40 ÷ 5 = 8
Value of
r = 8 cm
Answer(s): (a) (5
r + 13) cm; (b) 8 cm