Math 6: Decimal Operations Unit

1. Know Precise Vocabulary: Addends, Sum, Difference, Factors, Products, Dividend, Divisor, Quotient, as well as the name of the decimal spaces (tenths, hundredths, etc.)

2. Know how to tell if your answer makes sense. Be able to place a decimal in the given answer to a decimal problem without doing the math.

(ie: 2.5 x .3 would be less than 2.5 (so could not be 7.5, 75, etc.)

3. Know HOW and WHEN to ADD and SUBTRACT multi-digit numbers with and without decimals.

A. HOW to ADD & SUBTRACT: Line all decimals up , Drop decimal down, Add or subtract.

i. WHEN to ADD:

• • • • • • When looking for the total or sum

ii. WHEN to SUBTRACT:

• • • • • • When looking for the difference,

          • When comparing distance, speed, length, money, or any amount

          • When looking for "what's left" after taking off an amount.

4. Know HOW and WHEN to DIVIDE multi-digit numbers with and without decimals.

A. HOW: (steps 1 and 2 may not need to happen)

1) Move any visible decimal in the outside # to the end,

2) Move the dec. of the inside # the exact same spaces DO NOT MOVE THE DECIMAL IF THERE WAS NO VISIBLE DECIMAL IN THE OUTSIDE NUMBER.

3) Place a decimal on the answer bar directly above the decimal in the inside #. (If it is "invisible", put one at the end, and bring it up.)

**Place a digit (even if it's a ZERO) on the answer bar over any digit that is AFTER the decimal point or between numbers.

**If you "run out of digits to "bring down", add as many zeros as you need if you have a remainder to turn into a decimal. (Round if it does not terminate.)

i. WHEN to DIVIDE:

• • • • • When looking for a total after buying multiple items, working multiple hours, driving multiple miles, using a unit rate multiple times, etc.

2. Know HOW and WHEN to MULTIPLY multi-digit numbers with and without decimals.

A. HOW: Multiply factor digits as if there are no decimals, Total the number of digits AFTER decimal in the factors, Place the decimal in the product so that there are the same number of digits after the decimal.

i. WHEN to MULTIPLY:

• • • • • When looking for a total after buying multiple items, working multiple hours, driving multiple miles, using a unit rate multiple times, etc.