Fluently add, subtract, multiply, and divide multi-digit decimals

What you'll learn

1. Add and subtract multi-digit decimals using the standard algorithm by aligning decimal points (and therefore place values).
2. Multiply multi-digit decimals using the standard algorithm -- multiply the digits as if they were whole numbers, then place the decimal point so the product has the sum of the factors' decimal-place counts.
3. Divide a multi-digit decimal by a whole number using the standard long-division algorithm, placing the decimal point in the quotient directly above the dividend's decimal point.
4. Divide a multi-digit decimal by a decimal divisor by shifting both decimal points the same number of places to convert the problem to a whole-number-divisor case.
5. Estimate decimal computations using rounding to confirm reasonableness and catch decimal-point misplacement before submitting an answer.