Percent Change = New Value − Old Value|Old Value| × 100%
Example: There were 200 customers yesterday, and 240 today:
240 − 200|200|× 100% = 40200 × 100% = 20%
A 20% increase.
Percent Error = |Approximate Value − Exact Value||Exact Value| × 100%
Example: I thought 70 people would turn up to the concert, but in fact 80 did!
|70 − 80||80| × 100% = 1080 × 100% = 12.5%
I was in error by 12.5%
(Without using the absolute value, the error is −12.5%, meaning I under-estimated the value)
The difference between the two is that one states factual calculations and the other is a theoretical guess
Answer: 18
Step-by-step explanation: The formula for calculating a triangle’s area is 1/2(base•height). This means that 12•3 is 36, which multiplied by 1/2 is 18.
(Hope this helps)
Step-by-step explanation:
Arithmetic mean

18 and 35. The numbers whose sum 53 are 18 and 35.
The key to solve this problem is using a system of equations.
There are two numbers whose sum is 53. This number can be represented as x and y. So:
x + y = 53
Three times the smaller number is equal to 19 more than the larger. Let's set x as the smaller number and y the larger number. So:
3x = 19 + y
Clear y in both equations and let's use the equalization method to solve for x:
y = 53 - x and y = 3x - 19
Then,
53 - x = 3x - 19
53 + 19 = 3x + x ---------> 3x + x = 53 + 19 -------> 4x = 72
x = 72/4 = 18
To find y, let's substitute x = 18 in the equation x + y = 53
18 + y = 53 --------> y = 53 - 18
y = 35