Question

\(c)\dfrac{11}{1.4}+\dfrac{11}{4.7}+\dfrac{11}{7.10}+...\dfrac{11}{61.63}\)

Answer 1

`3.11/(1.4) + 11/4.7 + ... + 11/(61.64)`

`= 3.(11/(1.4) + 11/4.7 + ... + 11/(61.64))`

`= 11.(3/(1.4) + 3/4.7 + ... + 3/(61.64))`

`= 11.(1 -1/4 + 1/4 - 1/7 + ... + 1/61 - 1/64)`

`= 11.(1 - 1/64)`

`= 11.63/64`

`= 693/64:3`

`= 231/64`

sửa đề đề viết nhầm.

Answer 2

Sửa đề: 11/1*4+11/4*7+...+11/61*64

=11/3(3/1*4+3/4*7+...+3/61*64)

=11/3(1-1/4+1/4-1/7+...+1/61-1/64)

=11/3*63/64

=11*21/64=231/64