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| 1. |
The sum s of first five even natural number is given s=n(n+1) . find n if sum is 420 |
| Answer» s=n(n+1420 = n(n+1)n2+n- 420=0n2+21n - 20n - 420 =0n(n+21) - 20(n+21)=0n-20 = 0 or n+21=0 but n cannot be -vethus n=20check your answer s = 20(20+1)=21x20=420 | |