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Question:

An emergency room patient’s heart rate dropped 30% to 63 beats per minute. What was the patient’s heart rate prior to the drop in beats per minute?

A 90
explanation


Step 1: Interpret the Problem
Calculating the patient’s original heart rate before the drop requires some manipulation of the percentages. We need to consider that the original heart rate represents 100%. If the original heart rate represents 100% we must calculate how much of the original heart rate is remaining after a percent drop.
Given the heart rate dropped by 30%, we know,
100% – 30% = 70%
Therefore, the remaining heart rate percent is 70%.
Step 2: Turn The Percent Into a Decimal
We never use percentages in our actual math problems, so we first must turn our percentages into a decimal.
To turn a percentage into a decimal, we divide by 100, which is the same as moving the decimal point two spaces to the left.
70% = 70.%
70.% ÷ 100 = .70
70% as a decimal is .70. Remember, zeros at the end of a number after a decimal do not add any value, so we can just write it as .70.
.70 = .7
Step 3: Determine the Original Heart Rate
We know 63= 70%, and that we are looking for the value that represents 100%. This means whatever 100% is, will be more than 63.
Once you calculate the percent paid and turn that to a decimal, we can use the rule below to calculate the original price of an item by using division.
Current Heart Rate ÷ Decimal = Original Heart Rate
63 ÷ .7 = 90
The patient’s heart rate before the drop was 90 beats per minute.