Bài 3 Tính ( tính nhanh …)
a, $4.5^{2}$ – 81 . $3^{2}$
b,31.65+31.35-5000
c,$2^{2}$ .25.17+5.20.27+ $10^{2}$ . $5^{6}$
d,120 : {300:[150-($2.5^{3}$ – $2^{3}$ .25 )]}
Bài 3 Tính ( tính nhanh …)
a, $4.5^{2}$ – 81 . $3^{2}$
b,31.65+31.35-5000
c,$2^{2}$ .25.17+5.20.27+ $10^{2}$ . $5^{6}$
d,120 : {300:[150-($2.5^{3}$ – $2^{3}$ .25 )]}
Đáp án:
$\begin{array}{l}
a){4.5^2} – {81.3^2}\\
= 4.25 – 81.9\\
= 100 – 169\\
= – 69\\
b)31.65 + 31.35 – 5000\\
= 31.\left( {65 + 35} \right) – 5000\\
= 31.100 – 5000\\
= 3100 – 5000\\
= – 1900\\
c){2^2}.25.17 + 5.20.27 + {10^2}{.5^6}\\
= 4.25.17 + 100.27 + 100.125.125\\
= 100.\left( {17 + 27 + 125.125} \right)\\
= 100.15669\\
= 1566900\\
d)120:\left\{ {300:\left[ {150 – \left( {{{2.5}^3} – {2^3}.25} \right)} \right]} \right\}\\
= 120:\left\{ {300:\left[ {150 – \left( {2.5.25 – 8.25} \right)} \right]} \right\}\\
= 120:\left\{ {300:\left[ {150 – 25.\left( {10 – 8} \right)} \right]} \right\}\\
= 120:\left[ {300:\left( {150 – 25.2} \right)} \right]\\
= 120:\left[ {300:100} \right]\\
= 120:3\\
= 40
\end{array}$
a, 4.5^2 -81.3^2
=4.25-81.9
=100-729
=-629
b,31.65+31.35-5000
=31.(65+35)-5000
=31.100-5000
=3100-5000
=-1900
c,2^2.25.17+5.20.27+10^2.5^6
=4.25.17+5.20.27+100.15625
=100.17+100.27+100.15625
=100.(17+27+15625)
=100.15669
=1566900
d,120:{300:[150-(2.5^3-2^3.25)]}
=120:{300:[150-(2.125-8.25)
=120:{300:[150-(250-200)
=120:{300:[150-50]
=120:{300:100}
=120:3
=40