Đáp án:
`a)` `51/104`
`b)` `19/100`
`c)` `5/3`
Giải thích các bước giải:
`a)` `3/2.5 + 3/5.8 + 3/8.11 + ... + 3/101.104`
`=> 3. 1/3. (1/2 - 1/5 + 1/5 - 1/8 + 1/8 - 1/11 + ... + 1/101 - 1/104)`
`=> 1. (1/2 - 1/104)`
`=> 1. (52/104 + (-1)/104)`
`=> 1. 51/104`
`=> 51/104`
`b)` `1/30 + 1/42 + 1/56 + 1/9900`
`=> 1/5.6 + 1/6.7 + 1/7.8 + 1/99.100`
`=> 1/5 - 1/6 + 1/6 - 1/7 + 1/7 - 1/8 + ... + 1/99 - 1/100`
`=> 1/5 - 1/100`
`=> 20/100 + (-1)/100`
`=> 19/100`
`c)` `2^2/1.3 . 3^2/2.4 . 4^2/3.5 . 5^2/4.6`
`= (2.3.4.5)/(1.2.3.4) . (2.3.4.5)/(3.4.5.6)`
`= 5. 2/6`
`= 5/3`