Question

An aeroplane is 30m long and its model is 15cm long. If the total outer surface area of the model is 150cm², find the cost of painting the outer surface of the aeroplane at the rate of Rs.120 per sq. m. Given that 50sq. m. of the surface of the aeroplane is left for windows.

Answer 1

Given length of the plane = 30m = 3000cm
length of model = 15cm
Let surface area of plane be x cm²
Surface area of model = 150cm²
The ratio of the length = ratio of their surface area 
⇒3000:15 = x: 150
⇒15x = 150×3000
⇒x = 450000/15
∴x = 30000 cm²
∴Surface area of the plane = x = 30000cm² = 300m²
Given that 50m² of the surface of the plane is left for windows 
Total surfave area to be painted = 300m² - 50m² = 250m²
Given that cost to paint 1 m² = Rs120
Then to paint 250m² cost = 120 × 250 = 3000
∴Cost to paint the plane = Rs 3000

Answer 2

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