Question

tính

\(\dfrac{3}{1.4}+\dfrac{3}{4.7}+......+\dfrac{3}{91.94}\)

Answer 1

\(\dfrac{3}{1.4}\) + \(\dfrac{3}{4.7}\) + ... + \(\dfrac{3}{91.94}\)

= 1 - \(\dfrac{1}{4}\) + \(\dfrac{1}{4}\) - \(\dfrac{1}{7}\) + ... + \(\dfrac{1}{91}\) - \(\dfrac{1}{94}\)

= 1 - \(\dfrac{1}{94}\)

= \(\dfrac{93}{94}\)

Answer 2

\(\dfrac{3}{1.4}+\dfrac{3}{4.7}+....+\dfrac{3}{94.97}\)

= \(3.\left(1-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{7}+....+\dfrac{1}{94}-\dfrac{1}{97}\right)\)

= \(3.\left(1-\dfrac{1}{97}\right)\)

= \(3.\dfrac{96}{97}\)

= \(\dfrac{288}{97}\)

Answer 3

3/1.4 + 3/4.7 + ......... + 3/ 91.94

Bài làm:

= 1/ 1.4 + 1/4.7 + ......... + 1/91.94

= 1/1 - 1/4 + 1/4 - 1/7 + ............ + 1/91 - 1/94

= 1 - 1/94 = 93/94

Kết quả làm 93/94.

Chú ý: 93/94 là phân số.

Mình làm theo cách thầy cô dạy thôi .

Chúc các bạn làm bài tốt nhé.!!!

Answer 4

\(\dfrac{3}{1\cdot4}+\dfrac{3}{4\cdot7}+...+\dfrac{3}{91\cdot94}\\ =1-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{7}+...+\dfrac{1}{91}-\dfrac{1}{94}\\ =1-\dfrac{1}{94}\\ =\dfrac{93}{94}\)

Answer 5

$\frac{3}{1.4}+\frac{3}{4.7}+......+\frac{3}{91.94}$

= \(\dfrac{1}{1}\) \(-\) \(\dfrac{1}{4}\) \(+\) \(\dfrac{1}{4}\) \(-\) \(\dfrac{1}{7}\) \(+\) . . . . . \(+\) \(\dfrac{1}{91}\) \(-\) \(\dfrac{1}{94}\)

= \(\dfrac{1}{1}\) \(-\) \(\dfrac{1}{94}\)

= \(\dfrac{93}{94}\)

Answer 6

\(\dfrac{3}{1.4}\) \(+\) \(\dfrac{3}{4.7}\) \(+\) . . . . . \(+\) \(\dfrac{3}{91.94}\)

= \(\dfrac{1}{1}\) \(-\) \(\dfrac{1}{4}\) \(+\) \(\dfrac{1}{4}\) \(-\) \(\dfrac{1}{7}\) \(+\) . . . . . \(\dfrac{1}{91}\) \(-\) \(\dfrac{1}{94}\)

= \(\dfrac{1}{1}\) \(-\) \(\dfrac{1}{94}\)

= \(\dfrac{93}{94}\)