To solve this problem, we need to set up equations based on the given information. Let's define:
- \( c \) as the number of children
- \( a \) as the number of adults
- \( y \) as the number of youngsters
We have the following constraints:
1. The total number of passengers is 100.
\[
c + a + y = 100
\]
2. The total fare collected is 100 birr.
\[
0.1c + 2a + 1y = 100
\]
Now, we can solve these equations step-by-step.
First, let's multiply the second equation by 10 to eliminate the decimal:
\[
c + 20a + 10y = 1000
\]
Now we have:
\[
1. \quad c + a + y = 100
\]
\[
2. \quad c + 20a + 10y = 1000
\]
Subtract equation 1 from equation 2:
\[
(c + 20a + 10y) - (c + a + y) = 1000 - 100
\]
\[
19a + 9y = 900
\]
Let's simplify this equation:
\[
19a + 9y = 900
\]
Now, we solve this simplified equation. Since \(a\) and \(y\) must be whole numbers, we can look for integer solutions to this equation.
Let's solve for \(a\) in terms of \(y\):
\[
a = \frac{900 - 9y}{19}
\]
\(900 - 9y\) must be divisible by 19. Let's find the value of \(y\) that satisfies this:
\[
900 - 9y \equiv 0 \mod 19
\]
\[
900 \equiv 9y \mod 19
\]
\[
900 \mod 19 = 7
\]
\[
9y \equiv 7 \mod 19
\]
We need to find the modular inverse of 9 modulo 19. The inverse of 9 mod 19 is 17 (since \(9 \times 17 \equiv 1 \mod 19\)).
Now multiply both sides by 17:
\[
y \equiv 7 \times 17 \mod 19
\]
\[
y \equiv 119 \mod 19
\]
\[
y \equiv 5 \mod 19
\]
So \(y = 5\).
Substitute \(y = 5\) back into the equation for \(a\):
\[
a = \frac{900 - 9 \times 5}{19}
\]
\[
a = \frac{900 - 45}{19}
\]
\[
a = \frac{855}{19}
\]
\[
a = 45
\]
Now, substitute \(a = 45\) and \(y = 5\) back into the equation for the total number of passengers:
\[
c + 45 + 5 = 100
\]
\[
c = 100 - 50
\]
\[
c = 50
\]
So, the bus carries:
- 50 children
- 45 adults
- 5 youngsters
May 26, 2024