If you can multiply numbers you can multiply decimals. It is only a matter of, once you have multiplied two numbers, of counting the number of decimal places.

Example:

0.3*0.2

3*2=6

0.1 has one number after the decimal point and 0.2 has one number after the decimal point so there are two numbers after the decimal point in the answer.

The anser is 0.06

Example

0.29*27

* |
20 |
9 |

20 |
400 |
180 |

7 |
140 |
63 |

400+180+140+63=783. In the question there are two numbers after the decimal point for 0.29 and two numbers after the decimal point for 0.27 so there will be four numbers after the decimal point in the answer. The answer is 0.0783.

420*0.232

* |
400 |
20 |
0 |

200 |
80000 |
4000 |
0 |

30 |
12000 |
600 |
0 |

2 |
800 |
40 |
0 |

80000+4000+0+12000+600+0+800+40+0=97440

In the question there are no numbers after the decimal point for the 420 and there are three numbers after the decimal point for the 0.232 so there are three numbers after the decimal point in the answer. The answer is 97.440=97.44

43000*0.059

* |
40000 |
3000 |
0 |
0 |
0 |

50 |
2000000 |
150000 |
0 |
0 |
0 |

9 |
360000 |
27000 |
0 |
0 |
0 |

2000000+150000+360000+27000=2537000

There are no numbers after the decimal point for 43000 and 3 numbers after the decimal point for 0.059 so there are three numbers after the decimal point in the answer. The answer is 2537.000=2537