Four million writes 4000000, eight hundred thousand writes 800000, fifty thousand writes 50000, and three thousand writes 3000.

Solution: Because 4 million can be expressed as,

Four million =4x 1000000=4000000.

Similarly,

Eight hundred thousand =8x 100000=800000.

Fifty thousand =5x 10000=50000.

Three thousand =3x 1000=3000.

That is, 4 million writes, 800,000 writes, 800,000 writes, 50,000 writes and 3,000 writes.

Extended data:

Conversion between Counting Units and Counting Units

1, commonly used counting units are, ten, hundred, thousand, ten thousand, hundred thousand, one million, ten million, one hundred million.

2. Conversion relationship between counting units

1 million = 10x 1 ten thousand, 1 ten thousand = 1 ten thousand,1ten thousand =10x/0.

1K = 10x 1K， 1K = 10x 10， 10 = 10x 1。

Baidu encyclopedia-counting unit