Time taken by jerry alone is 10.1 hours
Time taken by callie alone is 8.1 hours
<u>Solution:</u>
Given:- For a certain prospectus Callie can prepare it two hours faster than Terry can
Let the time taken by Terry be "a" hours
So, the time taken by Callie will be (a-2) hours
Hence, the efficiency of Callie and Terry per hour is ![\frac{1}{a-2} \text { and } \frac{1}{a} \text { respectively }](https://tex.z-dn.net/?f=%5Cfrac%7B1%7D%7Ba-2%7D%20%5Ctext%20%7B%20and%20%7D%20%5Cfrac%7B1%7D%7Ba%7D%20%5Ctext%20%7B%20respectively%20%7D)
If they work together they can do the entire prospectus in five hours
![\text {So, } \frac{1}{a-2}+\frac{1}{a}=\frac{1}{5}](https://tex.z-dn.net/?f=%5Ctext%20%7BSo%2C%20%7D%20%5Cfrac%7B1%7D%7Ba-2%7D%2B%5Cfrac%7B1%7D%7Ba%7D%3D%5Cfrac%7B1%7D%7B5%7D)
On cross-multiplication we get,
![\frac{a+(a-2)}{(a-2) \times a}=\frac{1}{5}](https://tex.z-dn.net/?f=%5Cfrac%7Ba%2B%28a-2%29%7D%7B%28a-2%29%20%5Ctimes%20a%7D%3D%5Cfrac%7B1%7D%7B5%7D)
![\frac{2 a-2}{(a-2) \times a}=\frac{1}{5}](https://tex.z-dn.net/?f=%5Cfrac%7B2%20a-2%7D%7B%28a-2%29%20%5Ctimes%20a%7D%3D%5Cfrac%7B1%7D%7B5%7D)
On cross multiplication ,we get
![\begin{array}{l}{5 \times(2 a-2)=a \times(a-2)} \\\\ {10 a-10=a^{2}-2 a} \\\\ {a^{2}-2 a-10 a+10=0} \\\\ {a^{2}-12 a+10=0}\end{array}](https://tex.z-dn.net/?f=%5Cbegin%7Barray%7D%7Bl%7D%7B5%20%5Ctimes%282%20a-2%29%3Da%20%5Ctimes%28a-2%29%7D%20%5C%5C%5C%5C%20%7B10%20a-10%3Da%5E%7B2%7D-2%20a%7D%20%5C%5C%5C%5C%20%7Ba%5E%7B2%7D-2%20a-10%20a%2B10%3D0%7D%20%5C%5C%5C%5C%20%7Ba%5E%7B2%7D-12%20a%2B10%3D0%7D%5Cend%7Barray%7D)
<em><u>using quadratic formula:-</u></em>
![x=\frac{-b \pm \sqrt{b^{2}-4 a c}}{2 a}](https://tex.z-dn.net/?f=x%3D%5Cfrac%7B-b%20%5Cpm%20%5Csqrt%7Bb%5E%7B2%7D-4%20a%20c%7D%7D%7B2%20a%7D)
![x=\frac{12 \pm \sqrt{144-40}}{2}](https://tex.z-dn.net/?f=x%3D%5Cfrac%7B12%20%5Cpm%20%5Csqrt%7B144-40%7D%7D%7B2%7D)
![\begin{array}{l}{x=\frac{12 \pm \sqrt{144-40}}{2}} \\\\ {x=\frac{12 \pm \sqrt{104}}{2}} \\\\ {x=\frac{12 \pm 2 \sqrt{26}}{2}} \\\\ {x=6 \pm \sqrt{26}=6 \pm 5.1} \\\\ {x=10.1 \text { or } x=0.9}\end{array}](https://tex.z-dn.net/?f=%5Cbegin%7Barray%7D%7Bl%7D%7Bx%3D%5Cfrac%7B12%20%5Cpm%20%5Csqrt%7B144-40%7D%7D%7B2%7D%7D%20%5C%5C%5C%5C%20%7Bx%3D%5Cfrac%7B12%20%5Cpm%20%5Csqrt%7B104%7D%7D%7B2%7D%7D%20%5C%5C%5C%5C%20%7Bx%3D%5Cfrac%7B12%20%5Cpm%202%20%5Csqrt%7B26%7D%7D%7B2%7D%7D%20%5C%5C%5C%5C%20%7Bx%3D6%20%5Cpm%20%5Csqrt%7B26%7D%3D6%20%5Cpm%205.1%7D%20%5C%5C%5C%5C%20%7Bx%3D10.1%20%5Ctext%20%7B%20or%20%7D%20x%3D0.9%7D%5Cend%7Barray%7D)
If we take a = 0.9, then while calculating time taken by callie = a - 2 we will end up in negative value
Let us take a = 10.1
So time taken by jerry alone = a = 10.1 hours
Time taken by callie alone = a - 2 = 10.1 - 2 = 8.1 hours