Question: Exercise 1.1. Model the following real-life situations using algebraic expressions:
1. Romel's age 15 years ago
2. The amount of money left with Beatrice after buying her snacks worth 150
3. The total amount of pencils bought at 10 each
4. The number of students in a class whose total weight is 845 kilograms
5. The total amount donated by NGOs to the typhoon victims consisting of 1000-bills and 500-bills
1. **Problem:** Model Romel's age 15 years ago.
Let $r$ be Romel's current age.
The expression for Romel's age 15 years ago is:
$$r - 15$$
2. **Problem:** Model the amount of money left with Beatrice after buying snacks worth 150.
Let $b$ be the amount of money Beatrice initially had.
The amount left after buying snacks worth 150 is:
$$b - 150$$
3. **Problem:** Model the total amount of pencils bought at 10 each.
Let $p$ be the number of pencils bought.
The total cost is:
$$10 \times p = 10p$$
4. **Problem:** Model the number of students in a class whose total weight is 845 kilograms.
Let $s$ be the number of students.
Assuming each student weighs the same average weight $w$, then:
$$s \times w = 845$$
If $w$ is known, then the number of students is:
$$s = \frac{845}{w}$$
5. **Problem:** Model the total amount donated by NGOs to the typhoon victims consisting of 1000-bills and 500-bills.
Let $x$ be the number of 1000-bills and $y$ be the number of 500-bills.
The total amount donated is:
$$1000x + 500y$$
These algebraic expressions model the given real-life situations clearly and can be used to solve related problems.