Question

If you can buy $3$lbs of apples for $\$7.20$ , how many pounds of apples can you buy if you have $\$12.00?$

Answer 1

Hint: For these kinds of questions, all we need to make use of simple mathematics and cross-multiplying. We already know the cost of $3$lbs of apples which $\$7.20$. So if we divide $\$7.20$ by $3$ , we will get the cost of each lb. And now, we have to know the relation between lbs and pounds. If there is any conversion between, we either have to multiply or divide accordingly and convert into lbs. As we know the cost of $1$ lbs, we can easily find out how many lbs we will get for $\$12.00$.

Complete step by step solution:
Now let us divide the cost of $3$ lbs of apples which is $\$7.20$ by $3$ to know the cost of each lbs.
Upon doing so, we get the following :
$\Rightarrow \dfrac{\$7.20}{3}=\$2.4$.
So the cost of each lbs of apples is $\$2.4$.
Now let us get to know the relation between lbs and pounds.
We know that $1$ lbs = $1$ pound. So the cost of $1$ lbs will be equal to the cost of $1$ pound.
Since we got the relation, let us see how many pounds or lbs we will get for $\$12.00$.
We know that $\$2.4$will give us $1$ pound or $1$ lbs. Let the number of pounds or lbs we would get for $\$12.00$ be $x$.
Mathematically we can write this as follows :
$\Rightarrow \$2.4\times x=\$12$
Since the number of pounds or lbs multiplied by the cost of $1$ pound or $1$lbs will be equal to $\$12.00$.
Now let us solve for $x$ .
Upon doing so, we get the following :
$\begin{align}
  & \Rightarrow \$2.4\times x=\$12\\&\Rightarrow x=\dfrac{120}{24}=5\\\end{align}$
$\therefore $ Hence, if you can buy $3$lbs of apples for $\$7.20$ , we can buy $5$pounds or lbs of apples if you have $\$12.00$ .

Note: It is very important to remember all the constants for all the conversions. Some important conversions which are required for the exam are meters to centimeters, kilograms to grams, hours to seconds, liters to milliliters etc and vice-versa. We should remember all of these so as to be able to convert and do a sum quickly in the exam. We should be careful while calculating as there is a lot of scope of calculation errors.