Giải thích các bước giải:
Ta có:
\(\begin{array}{l}
5.2)\\
18.27 + 73.49 - 73.31\\
= 18.27 + 73.\left( {49 - 31} \right)\\
= 18.27 + 73.18\\
= 18.\left( {27 + 73} \right)\\
= 18.100\\
= 1800\\
7,\\
18.75 + 18.49 - 18.24\\
= 18.\left( {75 + 49 - 24} \right)\\
= 18.\left( {124 - 24} \right)\\
= 18.100\\
= 1800\\
7.1)\\
9.28 + 79.9 - 9.7\\
= 9.\left( {28 + 79 - 7} \right)\\
= 9.\left( {107 - 7} \right)\\
= 9.100 = 900\\
8.2)\\
75.14 + 75.5 + 19.25\\
= 75.\left( {14 + 5} \right) + 19.25\\
= 75.19 + 19.25\\
= 19.\left( {75 + 25} \right)\\
= 19.100 = 1900\\
8.3)\\
25.9 + 75.40 + 25.31\\
= 25.\left( {9 + 31} \right) + 75.40\\
= 25.40 + 75.40\\
= 40.\left( {25 + 75} \right)\\
= 40.100 = 4000\\
1.4)\\
49.75 + 75.52 - 75\\
= 75.\left( {49 + 52 - 1} \right)\\
= 75.100 = 7500\\
2.2)\\
74.19 + 74.81 + 26.49 + 26.51\\
= \left( {74.19 + 74.81} \right) + \left( {26.49 + 26.51} \right)\\
= 74.\left( {19 + 81} \right) + 26.\left( {49 + 51} \right)\\
= 74.100 + 26.100\\
= 100.\left( {74 + 26} \right)\\
= 100.100 = 10000\\
4)\\
47.\left( {20 + 55} \right) + 53.\left( {20 + 55} \right)\\
= 47.75 + 53.75\\
= 75.\left( {47 + 53} \right)\\
= 75.100\\
= 7500
\end{array}\)
