Bài 27 trang 10 SBT toán 6 tập 2

Đề bài

Rút gọn:

a) \(\displaystyle{{4.7} \over {9.32}}\)                                b) \(\displaystyle{{3.21} \over {14.15}}\)

c) \(\displaystyle{{2.5.13} \over {26.35}}\)                             d) \(\displaystyle{{9.6-9.3} \over {18}}\)

e) \(\displaystyle{{17.5-17} \over {3-20}}\)

f) \(\displaystyle{{49+7.49} \over {49}}\)

Lời giải chi tiết

a) \(\displaystyle{{4.7} \over {9.32}} = {{4.7} \over {9.4.8}} = {7 \over {9.8}} = {7 \over {72}}\)

b) \(\displaystyle{{3.21} \over {14.15}} = {{3.3.7} \over {2.7.3.5}} = {3 \over {2.5}} = {3 \over {10}}\)

c) \(\displaystyle{{2.5.13} \over {26.35}} = {{2.5.13} \over {2.13.5.7}} = {1 \over 7}\)

d) \(\displaystyle{\rm{}}{{9.6 - 9.3} \over {18}} = {{9.(6 - 3)} \over {9.2}} = {{6 - 3} \over 2} \)\(\displaystyle= {3 \over 2}\)

e) \(\displaystyle{\rm{}}{{17.5 - 17} \over {3 - 20}} = {{17.(5 - 1)} \over { - 17}} = {{5 - 1} \over { - 1}} \)\(\displaystyle=  - 4\)

f) \(\displaystyle{{49 + 7.49} \over {49}} = {{49.(1 + 7)} \over {49}} \)\(\displaystyle= 1 + 7 = 8\)