Tom bought 5 apples and 4 pears for $3.80. Jerry bought 10 apples & 5 pears. Jerry paid with a $10 bill and got $3.90 back as change. How much is 1 pear?
Let the cost of 1 apple be a and the cost of 1 pear be p.
Tom's purchase can be represented by the equation 5a + 4p = 3.80. Equation 1
Jerry's purchase can be represented by the equation 10a + 5p = 10.00 - 3.90 = 6.10. Equation 2
Multiplying equation 1 by 2 gives 10a + 8p = 2(3.80) = 7.60. Equation 3
Subtracting equation 2 from equation 3 gives 10a + 8p - 10a - 5p = 7.60 - 6.10.
This simplifies to 3p = 1.50
Finally, divide both sides by 3 to isolate p: p = 1.50/3 = $<<1.50/3=0.50>>0.50.
Therefore, one pear costs $0.50. Answer: \boxed{0.50}.