By tens, hundreds, thousands

Find the value of forty seven times twenty without using a calculator. Try it first. Pause if you like. Twenty is two times ten. We must multiply by both factors. First, forty seven times two is ninety four. Keep the times ten. Ninety four times ten is nine hundred and forty. Every digit moves one place to the left. The zero holds the ones place. Ten means one place, one hundred means two places, and one thousand means three places. A multiple has two factors. Both belong in the calculation.

Find the value of two hundred and forty thousand divided by eight thousand without using a calculator. Try it first. Pause if you like. Eight thousand is one thousand times eight. Divide by one thousand first, then by eight. Two hundred and forty thousand divided by one thousand is two hundred and forty. Dividing by one thousand means three places to the right. The divide by eight is still there. Two hundred and forty is twenty four tens. Twenty four divided by eight is three, so twenty four tens divided by eight is three tens. Three tens is thirty. Two hundred and forty divided by eight is thirty. The power of ten is only one factor. The other factor is still part of the divisor.

Find the value of five thousand, six hundred divided by four hundred without using a calculator. Try it first. Pause if you like. Four hundred is one hundred times four. Divide by one hundred and then by four. Five thousand six hundred divided by one hundred is fifty six. Two places to the right is division by one hundred. We still have to divide by four. Fifty six divided by four is fourteen. To multiply or divide by a multiple of ten, split it into two factors and use both.