2. จงหาผลลัพธ์แต่ละข้อต่อไปนี้ในรูปสัญกรณ์วิทยาศาสตร์
1) \(\mathtt{(2 \times 10^6) \div (4 \times 10^3)}\)
วิธีทำ
\(\mathtt{(2 \times 10^6) \div (4 \times 10^3)}\) = \(\mathtt{\dfrac{2 \times 10^6}{4 \times 10^3}}\)
= \(\mathtt{\dfrac{1}{2} \times 10^{6 \, – \, 3}}\)
= \(\mathtt{0.5 \times 10^3}\)
= \(\mathtt{\dfrac{5}{10} \times 10^3}\)
= \(\mathtt{5 \times \dfrac{10^3}{10}}\)
= \(\mathtt{5 \times 10^{3 \, – \, 1}}\)
= \(\mathtt{5 \times 10^2}\)
ตอบ \(\mathtt{5 \times 10^2}\)
2) \(\mathtt{(2.84 \times 10^{-7}) \div (4 \times 10^5)}\)
วิธีทำ
\(\mathtt{(2.84 \times 10^{-7}) \div (4 \times 10^5)}\) = \(\mathtt{\dfrac{2.84 \times 10^{-7}}{4 \times 10^5}}\)
= \(\mathtt{0.71 \times 10^{-7 \, – \, 5}}\)
= \(\mathtt{\dfrac{71}{100} \times 10^{-12}}\)
= \(\mathtt{\dfrac{7.1 \times 10}{10^2} \times 10^{-12}}\)
= \(\mathtt{7.1 \times \dfrac{10}{10^2} \times 10^{-12}}\)
= \(\mathtt{7.1 \times 10^{1 \, – \, 2} \times 10^{-12}}\)
= \(\mathtt{7.1 \times 10^{-1} \times 10^{-12}}\)
= \(\mathtt{7.1 \times 10^{-1 \, + \, (-12)}}\)
= \(\mathtt{7.1 \times 10^{-13}}\)
ตอบ \(\mathtt{7.1 \times 10^{-13}}\)
3) \(\mathtt{\dfrac{(2.4 \times 10^3) \times (8 \times 10^{-5})}{3 \times 10^7}}\)
วิธีทำ
\(\mathtt{\dfrac{(2.4 \times 10^3) \times (8 \times 10^{-5})}{3 \times 10^7}}\) = \(\mathtt{\dfrac{2.4 \times 8 \times 10^3 \times 10^{-5}}{3 \times 10^7}}\)
= \(\mathtt{\dfrac{0.8 \times 8 \times 10^{3 \, + \, (-5)}}{10^7}}\)
= \(\mathtt{\dfrac{6.4 \times 10^{-2}}{10^7}}\)
= \(\mathtt{6.4 \times 10^{-2 \, – \, 7}}\)
= \(\mathtt{6.4 \times 10^{-9}}\)
ตอบ \(\mathtt{6.4 \times 10^{-9}}\)
4) \(\mathtt{0.000000000081 \div 900}\)
วิธีทำ
\(\mathtt{0.000000000081 \div 900}\) = \(\mathtt{\dfrac{81}{1,000,000,000,000} \div (9 \times 100)}\)
= \(\mathtt{\dfrac{81}{10^{12}} \div (9 \times 10^2)}\)
= \(\mathtt{\dfrac{81}{10^{12}} \times \dfrac{1}{9 \times 10^2}}\)
= \(\mathtt{\dfrac{81}{9 \times 10^{12 \, + \, 2}}}\)
= \(\mathtt{\dfrac{9}{10^{14}}}\)
= \(\mathtt{9 \times \dfrac{1}{10^{14}}}\)
= \(\mathtt{9 \times 10^{-14}}\)
ตอบ \(\mathtt{9 \times 10^{-14}}\)