Finding the unknown (4 operations) II
Simplifying the problem
We have seen how to solve number problems with missing values, but so far, we've looked at problems with only one step. When we have more than one part to our number problem, it helps to simplify things first. Then, once we've done that, we can work out the missing number. In Video 1, we look at problems with more than one part, and identify which parts to solve first. Then, we look at how to find the value of the variable, or letter, that's used to signal the missing value.
Other types of problems
Sometimes you might have a problem with missing values, but it looks a little different. By thinking of a number problem, you can still find the missing values. What could we do if our problem looked like this?
In this circle, we need to find the value of the missing angle, or h. How can we do this, using number problems? Let's take a look, in Video 2.
Even if it our problem looks a little different, we can still find missing values. By writing out our number problem, we may also be able to simplify our problem, and solve one part first. Then, we can find the missing value.
Examples
Question 1
We want to work out the value of $d$d that makes the following equation true:
$8+5\times d=28$8+5×d=28
First let's complete a simpler expression. Fill in the blank in the equation below.
$8+\editable{}=28$8+=28
So $5\times d=20$5×d=20. What number times $5$5 equals $20$20?
QUESTION 2
Let's work out what $n$n must equal to make the following equation true.
$28\div4=n-3$28÷4=n−3
First, let's calculate the left hand side, $28\div4$28÷4.
So now we have $7=n-3$7=n−3. What is the value of $n$n?