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5.Find the total area of 12 squares whose sides are 12cm, 13cm, 23 cmsrespectively.Ans: 3818cm2 |
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Answer» Area of square = (side length)² There are 12 squares whose sides are 12, 13, 14, ........ 23 so, area of square are 12² , 13² , 14² , .......23² we know, sum of square of natural number = n(n +1)(2n+1)/6 12² + 13² + ......23² = (1² + 2² + 3² + ..... + 23²) - (1² + 2² + ..... 11²)= S₂₃ - S₁₁= 23(23 + 1)(23 × 2 + 1)/6 - 11(11 + 1)(11 × 2 + 1)/6 = (23 x 24 x 47)/6 - (11 x 12 x 23)/6= 4324 - 506= 3818 |
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