[tex]$10\%$[/tex] of a villager's cows died in [tex]$2011$[/tex]. [tex]$12 \frac{1}{2} \%$[/tex] of the remaining cows died in [tex]$2012$[/tex]. If the remaining cows are [tex]$63$[/tex], how many cows did the villager have originally?



Answer :

Let's solve this problem step-by-step.

1. Step 1: Define the initial number of cows.
Let the initial number of cows be [tex]\( x \)[/tex].

2. Step 2: Calculate the cows remaining after 10% died.
If 10% of the cows died in the first year, then 90% of the cows are still alive.
[tex]\[ \text{Remaining cows after the first year} = 0.9 \times x \][/tex]

3. Step 3: Calculate the cows remaining after 12.5% of the remaining cows died in the second year.
12.5% of the remaining cows die in the second year. To find the number of cows that died in the second year, we need 12.5% of the cows remaining after the first year.
[tex]\[ \text{Cows died in the second year} = 0.125 \times (0.9 \times x) \][/tex]
Therefore, the cows left after the second year are:
[tex]\[ \text{Remaining cows after the second year} = (0.9 \times x) - (0.125 \times 0.9 \times x) \][/tex]
Simplify:
[tex]\[ \text{Remaining cows after the second year} = 0.9x - 0.1125x = 0.7875x \][/tex]

4. Step 4: Set up the equation using the given final number of cows.
According to the problem, after both years, there are 63 cows remaining.
[tex]\[ 0.7875x = 63 \][/tex]

5. Step 5: Solve for [tex]\( x \)[/tex].
[tex]\[ x = \frac{63}{0.7875} \][/tex]
Calculate:
[tex]\[ x = 80 \][/tex]

So, the villager originally had [tex]\( 80 \)[/tex] cows.