The algorithm of this topic is wrong. In the end, you can't add your own ten dollars. You should add the twenty dollars returned to your parents. The ten dollars saved can't be added to the arrears.

It should be 490+490+20= 1000 yuan, and the calculation is correct.

In fact, there is a trap here, that is, the remaining ten dollars. This is a smoke bomb that confuses the questioner's thinking. Actually, it's useless Aside from this figure, it is actually returned to Mom and Dad 20 yuan first, so it still owes 980 yuan, 490+490=980, so the figure is correct.

Extended data:

Elementary school arithmetic skills

Multiplication of ten digits

Formula: head joint, tail to tail, tail to tail.

Formula and algorithm:/kloc-0 /×1=12+4 = 62× 4 = 8.

Answer: 12× 14= 168.

Note: Numbers are multiplied. If two digits are not enough, use 0 to occupy the space. The number multiplication is a two-digit number, remember to add it to the previous one!

This method requires children to try many times, and parents should encourage their children to master it skillfully. This way, children can be one step ahead when they study!