Here's a tax bracket question used to illustrate forming formulas.
Suppose tax brackets are as follows: for taxable income between $0 to $32000, the tax rate is 15%; for taxable income between $32000 to $64000, the tax rate is 22%; for taxable income between $64000 and $100000, the tax rate is 25%, for income above $100000, the tax rate is 29%.
a) If x is the taxable income, and T(x) is the tax, find a formula for tax up to $100000.
b) Plot the graph of taxation for taxable income up to $100000.
C) Write, in terms of T(x), the max taxation on the income between $64000 and $100000.
a) Because the taxation is separated into brackets, we have to separate the answer into "brackets" as well. First of all, for income below $32000, we pay 15% tax. So if income is x < $32000, then tax T(x) = 0.15x. At x = $32000, tax is . Now, if taxable income is between $32000 and $64000, only the portion of income above $32000 has to pay 22% of tax, (and the portion below $32000 would pay 15%, which amounts to $4800), then the tax . At x = 64000, tax = 4800 + (tax on portion above $32000). The tax on portion over $32000 is . So, at income x = 64000, tax = 4800 + 7040 = 11840. Now, turning to income > 64000, the tax .
b) If T(x) is on the vertical axis and x is on the horizontal axis, then we plot the following points (0, 0), (32000, 4800), (64000, 11840) and (100000, t), where t = tax you pay at $100000. Plug $100000 into formula . That is t = 20840.
c) The max tax between $64000 and $100000 is just T(100000) - T(64000) = 20840 - 11840 = 9000.