A number p is increased by 20%, then decrease by 10%. If the final value is 1 620, find the original value of p.
Mathematics
kelly1698
Question
A number p is increased by 20%, then decrease by 10%. If the final value is 1 620, find
the original value of p.
the original value of p.
2 Answer

1. User Answers Anonym
Increase something by its 20% means to consider its 120%:
[tex]p\mapsto p\cdot\dfrac{120}{100} = \dfrac{120p}{100}=\dfrac{6p}{5}[/tex]
Decrease something by its 10% means to consider its remaining 90%:
[tex]\dfrac{6p}{5}\mapsto \dfrac{6p}{5}\cdot\dfrac{90}{100}=\dfrac{540p}{500}=\dfrac{27p}{25}[/tex]
So, we have the equation
[tex]\dfrac{27p}{25}=1620 \iff 27p=40500 \iff p=1500[/tex]

2. User Answers Anonym
Answer:
1500.
Stepbystep explanation:
We can use algebra to do this.
20% = 0.20 and 10% = 0.10.
We form an equation:
p + 0.20p  0.10(p + 0.20p) = 1620
p + 0.20p  0.10p  0.02p = 1620
1.20p  0.12p = 1620
1.08p = 1620
p = 1620/1.08
= 1500.