Valerie wants to take out a discount loan of $569. the rate is 4.5% for 250 days. how much interest will she pay? (be sure to round the time to the nearest hundredth.

The interest is computed from

... I = Prt

where P is the principal amount ($569), r is the rate (0.045) and t is the time in years (250/360).

... I = $569×0.045×250/360 ≈ $17.78

Please note that time is not rounded. Rather, the exact value (25/36) is used in the calculation. The only rounding of any number is done at the end, where the amount is rounded to the nearest cent. (Your text authors should know this.)

If you follow the problem instructions (which Valerie's lender will not do), the interest is calculated as ...

... t = 250/360 = 0.6944444... ≈ 0.69 . . . . years

... I = $569×0.045×0.69 ≈ $17.67

Note the rounding of intermediate numbers (time) introduces an error of about $0.11 in the answer.

the mistake in the pattern is that :

b. the decimal point was moved one too many place values each time

the correct pattern could be made by :

b. moving the decimal point to the right the same numbers of place values as the exponents