Zara has forgotten her 4-digit PIN code.
1 answer:
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Answer:
The final amount if 784 is decreased by 1% followed by a 4% increase is 807.52.
Step-by-step explanation:
General Formula
<em>A way to solve this problem is as follows</em>:
The general formula for this is taking into account that:
The <em>starting point</em> is number 784.
The most important key is the solution for this answer is that:
Where <em>x</em> is a number that we need to find. Then
[1]
Is 784 increased or decreased after all?
We also need to evaluate the following: if a quantity decreases a percentage, and then increases in another percentage, what is the final percentage? In this case, we have first that 784 decreases by 1% and then increases by 4%. As a result 784 will +4% - 1% = +3%, that is, 784 will increase in 3%.
Finding the result
If 784 increases by 3%, we have:
Which is equal to
Solving for <em>x</em>, we first multiply by 784 to both sides of the previous formula:
Remember that if we add, subtract, multiply, divide... to both sides of the equation, we do not "alter" this equation.
Subtracting 784 to both sides:
Multiplying by -1 to both sides:
We have to remember that:
Then
Therefore, using formula [1], an increase of 3% is
Since an increase of 3% is 23.52, we have to add this to the starting point 784, and finally the amount is 784 + 23.52 = 807.52.
As a result, the final amount if 784 is decreased by 1% followed by a 4% increase is 807.52.
In a more <em>terse way</em> of solving this problem, we can say that:
Increase of 4% = 784 * 0.04 = 31.36.
Decrease of 1% = 784 * 0.01 = 7.84.
Difference = 31.36 - 7.84 = 23.52.
Then, we need to add this value to 784, and 784 + 23.52 = 807.52 (the same result).