A, 11+12+13+.....+28+29 C,1+3+5+.....+39
= (11+29)+(12+28)+...+20 = ( 39+1 )+( 37 + 3 ) + ... + (21+19)
= 40 + 40 + ... + 20 = 40 + 40 +... + 40
= 9 x 40 + 20 = 380 = 10 . 40 = 400
B,108.12+25.92+13.108 D,2+7+12+17+......+62
= 108 . (12+13) + 25 . 92 = ( 62+2 ) + ( 57+ 7 ) + .... +32
= 108 . 25 + 25 . 92 = 64 + 64 + ... + 32
= (108 + 92) . 25 = 64 . 6 + 32 = 416
= 200 . 25 = 5000