The weight in 1980 is [tex]\frac{4k}{5}[/tex] kilograms
Solution:
From 1980 to 1990, Lior’s weight increased by 25%
His weight is "k" kilograms in 1990
To find: weight in 1980
This is a percentage increase problem
Let "x" be the weight in kilograms in 1980
The percentage increase is given by formula:
[tex]\text{Percentage increase } = \frac{\text{Final value - initial value}}{\text{initial value}} \times 100[/tex]
Here,
Initial value in 1980 = x
Final value in 1990 = k
Percentage increase = 25 %
Substituting the values in formula,
[tex]25 = \frac{k-x}{x} \times 100\\\\25x = 100(k-x)\\\\x = 4(k-x)\\\\x = 4k - 4x\\\\5x = 4k\\\\x = \frac{4k}{5}[/tex]
Thus the weight in kilograms in 1980 is [tex]\frac{4k}{5}[/tex]
