Question

\((5+10+15+...+100): x = 70\)

Answer 1

`(5 + 10 + 15 + ... + 100) : x = 70`

Ta có:

`5+10+15+20+...+95+100`

`=100+(5+95)+(10+90)+...+(45+55) +50`

`=100 + 9 . 100 + 50`

`=150 + 900`

`=1050`

`=>` `1050 : x = 70`

`x = 1050 : 70`

`x = 15`

Vậy `x = 15`

Answer 2

{[100-5):5+1]x(100+5):2} : x = 70

{20x105:2} : x = 70

{105x10} : x =70

1050 : x= 70

x=15

x=1155:70

x=15