The whole surface area of a rectangular block is 846 sq.cm . Find its dimensions,if they are in the ratio 5:4:3.

Let length be 5x breadth be 4x and height of the block be 3x cm.

Total Surface Area of rectangle= 2(lb+bh+lh)

846=2(5x.4x+4x.3x+5x.3x)

846=2(20x²+12x²+15x²)

846=2(47x²)

846=94x²

846/94=x²

9=x²

x=+3

x cant be negative, x=3

l=15cm, b=12cm, h=9cm

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