The diagonals of a rhombus measure 18 cm and 14 cm. Find its area.

Class 8MensurationMensuration

Step-by-Step Solution

Area of a rhombus = ½ × d₁ × d₂ = ½ ×

18 \times 14 = 126 cm^{2}

. Trap

252 cm^{2}

: forgetting the ½. Trap

63 cm^{2}

: halving twice. Trap

32 cm^{2}

: adding the diagonals, which gives a length, not an area.

Answer: D)

126 cm^{2}

A cylinder is a circle stacked vertically. Two measurements: radius

r

and height

h

.

**Curved surface area (CSA) = 2π

r h

** (imagine 'unrolling' the curved surface — it becomes a rectangle of width 2π

r

and height h).

**Total surface area (TSA) = 2π

r^{2} + 2

r h = 2

r (r + h)

** (curved surface + two circular ends).

**Volume = π

r^{2}

h

** (area of circular base × height).

Use π = 22/7 when

r

is a multiple of 7; otherwise π ≈ 3.14.

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