# An box (open one) has a square base with sides of length x cm and a height of 10 cm. If the total surface area of the box is 225 cm2, find the length of the side of the square base of the box.

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by Akshata

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by Akshata

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The side: a*10=10a

10a*4+a²=40a+a²

40a+a²=225 /+400

40a+a²+400=625

(a+20)²=625/√ from both sides

a+20=25

a=5

The length of the side of the base is 5