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Question 11b

Video explanation ↓

The figure is made up of a rectangle PQUV, a square RSTU and a triangle PRT. QRU and VUT are straight lines. UT = 6 cm and QR = 4 cm. The perimeter of rectangle PQUV is 46 cm. Find the area of triangle PRT. (3 marks)

Question 11b diagram

Answer: 27 cm²

Workings

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perimeter PQUV = 46cm

since RSTU is a square

UT = ST = RU = 6cm

QU (breadth of rectangle) = QR + RU = 4 + 6 = 10cm

PQ is the length of rectangle

2 length + 2 breadth = perimeter

2 length + 2 breadth = 46 1 length + 1 breadth = 46 ÷ 2 = 23

1 breadth (QU) → 10 1 length (PQ) → 23 - 10 = 13 cm

shaded triangle → rectangle + square - (▵ D + ▵ C + ▵ E

rectangle area → 10 x 13 = 130 cm²

square area → 6 x 6 = 36 cm²

▵ D area → 1/2 x base x height = 1/2 x 19 x 10 = 95 cm²

▵ C area → 1/2 x base x height = 1/2 x 13 x 4 = 26 cm²

▵ E area → 1/2 x base x height = 1/2 x 6 x 6 = 18 cm²

shaded triangle → rectangle + square - (▵ D + ▵ C + ▵ E = 130 + 36 - (95 + 26 + 18) = 27 cm²

Video explanations

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