Toán Lớp 5: Tính nhanh
a ,4 x 113 x 25 – 5 x 112 x 20
b, 2021/2022 x 2/7 + 2021/2022 x 6/7 – 2021/2022 x 1/7
giúp mình với sắp nộp r ????????????????????
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Toán Lớp 5: Tính nhanh
a ,4 x 113 x 25 – 5 x 112 x 20
b, 2021/2022 x 2/7 + 2021/2022 x 6/7 – 2021/2022 x 1/7
giúp mình với sắp nộp r ????????????????????
Comments ( 2 )
a, 4 \times 113 \times 25 – 5 \times 112 \times 20\\
= 4 \times 25 \times 113 – 5 \times 20 \times 112\\
= 100 \times 113 – 100 \times 112\\
= 100 \times (113 – 112)\\
= 100 \times 1\\
= 100\\
————-\\
b, \dfrac{2021}{2022} \times \dfrac{2}{7} + \dfrac{2021}{2022} \times \dfrac{6}{7} – \dfrac{2021}{2022} \times \dfrac{1}{7}\\
= \dfrac{2021}{2022} \times (\dfrac{2}{7} + \dfrac{6}{7} – \dfrac{1}{7})\\
= \dfrac{2021}{2022} \times (\dfrac{8}{7} – \dfrac{1}{7})\\
= \dfrac{2021}{2022} \times \dfrac{7}{7}\\
= \dfrac{2021}{2022} \times 1\\
= \dfrac{2021}{2022}\\
\end{array}\)