Question 1: We have to identify which of given expressions are rational expressions.
1.
![3.12 * 1.4](https://img.qammunity.org/2019/formulas/mathematics/high-school/12snvewh6ehwyez1veyjq4dk2fzmeo3mm3.png)
= 4.368
=
![(4368)/(1000)](https://img.qammunity.org/2019/formulas/mathematics/high-school/16cbu0zvxyxbct3ihofe5zllwkqygoow1q.png)
This is expressed in the form of
where p and q are integers, where q is not equal to zero.
Hence, it is rational.
2.
![\sqrt 9 * \sqrt 25](https://img.qammunity.org/2019/formulas/mathematics/high-school/xzc56v05xkxuebk0w08ro7102e1ikwl45n.png)
=
![3 * 5](https://img.qammunity.org/2019/formulas/mathematics/high-school/ghnu339g5kw2rnr1jwswwmlo2rb4r0w4wf.png)
= 15
=
which is also expressed in the form of
where p and q are integers, where q is not equal to zero.
Hence, it is rational.
3.
![\sqrt 2 * \sqrt 3](https://img.qammunity.org/2019/formulas/mathematics/high-school/rxph0tg11kjd03ylzpy1lcjyv9659e9hkk.png)
=
![\sqrt 6](https://img.qammunity.org/2019/formulas/mathematics/high-school/cuj1nbkhck5fgcarar2efdn4vvawp94yp0.png)
which can not be expressed in the form of
where p and q are integers and q is not equal to zero.
Hence, it is not rational.
4. 4+5
= 9
=
which is also expressed in the form of
where p and q are integers, where q is not equal to zero.
Hence, it is rational.
5.
![n * 3](https://img.qammunity.org/2019/formulas/mathematics/high-school/3o89b9x29jpev06p2xmi8t5mlw1vq3z4gf.png)
This expression can be rational and can not be rational. It depends on the value of 'n'.
Question 2:
Molli purchased 9 apples for $3.96.
Then, Molli divided $3.96 by 9.
Since, the cost of 9 apples = $3.96
If we have to find the cost of 1 apple, then we will divide the cost of 9 apples by the number of apples purchased.
Therefore, Cost of 1 apple = $3.96
![/ 9](https://img.qammunity.org/2019/formulas/mathematics/high-school/nzpcirdimyqevwyey0zzyb8ou9g8qwmny2.png)
= 0.44
Therefore, Molli divided $3.96 by 9 in order to find out how much she paid per apple.
Therefore, Option 1 is the correct answer.