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प्रश्न
Find the sum of first 8 multiples of 3
उत्तर १
First, 8 multiples of 3 are { 3, 6, 9...,24}
We can observe they are in AP with first term (a) = 3 and last term (l) = 24 and number of terms are 8.
`S_n = n/2 (a + l)`
`=> S_n = 8/2(3 + 24)`
`S_8 = 4 xx (3 + 24) = 108`
Hence, the sum of the first 8 multiples of 3 is 108
उत्तर २
First 8 multiples of 3 are
3, 6, 9, 12, 15, 18, 21, 24
The above sequence is an A.P
a= 3, d= 3 and last term l = 24
`S_n = n/2 (a + 1) = 8/2[3 + 24] = 4(27)`
`S_n = 108`
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