so, she can type 50 words in 1 minute, well, 1 minute is 60 seconds, so she really can type 50 words in 60 seconds, hmmmm how many seconds does it take her for 1 word?
[tex]\bf \begin{array}{ccll}
words&seconds\\
\text{\textemdash\textemdash\textemdash}&\text{\textemdash\textemdash\textemdash}\\
50&60\\
1&s
\end{array}\implies \cfrac{50}{1}=\cfrac{60}{s}\implies s=\cfrac{1\cdot 60}{50}\implies s=\cfrac{6}{5}[/tex]
so, we know that 1 Jiffy is 1/100 of a second, so, how many Jiffies are there in 6/5 of a second then?
[tex]\bf \begin{array}{ccll}
jiffies&seconds\\
\text{\textemdash\textemdash\textemdash}&\text{\textemdash\textemdash\textemdash}\\
1&\frac{1}{100}\\\\
j&\frac{6}{5}
\end{array}\implies \cfrac{1}{j}=\cfrac{\quad \frac{1}{100}\quad }{\frac{6}{5}}\implies \cfrac{1}{j}=\cfrac{1}{100}\cdot \cfrac{5}{6}
\\\\\\
\cfrac{1}{j}=\cfrac{5}{600}\implies \cfrac{1\cdot 600}{5}=j\implies 120=j[/tex]
