Câu hỏi
Thực hiện phép tính:
\(\begin{array}{l}a)\,\,35 + 49 + 65 & & & & b)\,\,21.54 + 21.46 + ( - 2000)\\c)\,\,113 + \left| { - 39} \right| + ( - 2)& & & & d)\,\,90 - \left( {{{4.5}^2} - {{7.3}^2}} \right)\end{array}\)
- A \(\begin{array}{l}{\rm{a}})\,\,149\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,{\rm{b}})\,\,100\\{\rm{c}})\,\,150\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,{\rm{d}})\,\,53\end{array}\)
- B \(\begin{array}{l}{\rm{a}})\,\,145\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,{\rm{b}})\,\,200\\{\rm{c}})\,\,150\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,{\rm{d}})\,\,50\end{array}\)
- C \(\begin{array}{l}{\rm{a}})\,\,149\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,{\rm{b}})\,\, - 100\\{\rm{c}})\,\,154\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,{\rm{d}})\,\,53\end{array}\)
- D \(\begin{array}{l}{\rm{a}})\,\,149\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,{\rm{b}})\,\, - 100\\{\rm{c}})\,\,154\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,{\rm{d}})\,\,53\end{array}\)
Phương pháp giải:
- Thứ tự thực hiện các phép tính đối với biểu thức không có dấu ngoặc:
Lũy thừa \( \to \) Nhân và chia \( \to \) Cộng và trừ
- Thứ tự thực hiện các phép tính đối với biểu thức có dấu ngoặc:
\((\,\,)\,\, \to {\rm{[}}\,\,{\rm{]}}\,\, \to {\rm{\{ }}\,\,{\rm{\} }}\)
- \(\left| a \right| = a\) nếu \(a \ge 0\) và \(\left| a \right| = - a\) nếu \(a < 0\)
Lời giải chi tiết:
\(\begin{array}{l}a)\,\,35 + 49 + 65\,\,\,\,\,\,\,\,\,\,\,\,\\\,\,\,\,\,\, = (35 + 65) + 49\\\,\,\,\,\,\, = \,\,100 + 49\,\,\,\,\,\,\,\,\\\,\,\,\,\,\, = \,\,\,\,\,149\,\,\,\,\,\,\,\,\,\end{array}\)
\(\begin{array}{l}b)\,\,21.54 + 21.46 + ( - 2000)\\ = 21.(54 + 46) + ( - 2000)\\ = 21.100 + ( - 2000)\\ = 2100 + ( - 2000)\\ = \,\,\,\,100\end{array}\)
\(\begin{array}{l}c)\,\,113 + \left| { - 39} \right| + ( - 2)\,\,\,\,\,\,\,\,\\\,\,\,\,\, = 113 + 39 + ( - 2)\,\,\,\,\,\,\,\,\\\,\,\,\,\, = \,\,152 + ( - 2)\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\\\,\,\,\,\, = \,\,\,\,\,150\,\,\,\,\,\,\,\,\,\,\,\end{array}\)
\(\begin{array}{l}d)\,\,90 - \left( {{{4.5}^2} - {{7.3}^2}} \right)\\ = \,\,90 - (4.25 - 7.9)\\ = \,\,90 - (100 - 63)\\ = \,\,90 - 37\\ = \,\,53\end{array}\)
Chọn A.
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