Question

Calculati suma a 25 de numere consecutive stiind ca primul si al treilea numar sunt direct proportionale cu 10 si 14

Answer 1

25 nr consecutive: 
a, a+1, a+2, a+3, .........., a+24
a/10=(a+2)/14=k => a=10k si a+2=14k
scadem cele 2 relatii => a+2-a=14k-10k
=> 4k=2; k=1/2
a=10k=10/2
a=5 => a+1=6; a+2=7;.....;a+24=29
S=5+6+7+8+.........+29
S=25(5+29):2
S=25·34:2
S=25·17
S=425