Sum of the first 15 positive integers is 15*(15+1)/2 = 120
Sum of the first 15 multiples of 8 is 8*120 = 960
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5 + 10+15+20=50 ans
(1 x 8) + (2 x 8) = (1 + 2) x 8 = 3 x 8 = 24
Sum of first 25 multiples of 44+8+12....100taking 4 common4(1+2+3+4....+25) = 4*325 =1300
Well, the multiples of 8 go "8, 16, 24...etc." The first four multiples of 8 over 20 are 24, 32, 40, and 48. i) 24 + 32 = 56 ii) 56 + 40 = 96 iii) 96 + 48 = 144 Therefore the sum is 144.
8A + (8A+8) + (8A+16) = 888 24A + 24 = 888 ===> 24A = 864 ===> A = 36 The multiples are 8A, 8A+8, 8A+16 = 288, 296, 304. Sum = 888.