1. Find `321 * 78`
Solution:
| | 2 | 1 | | | `larr` | Carry of `321xxcolor{green}{7}` |
| | 2 | 1 | | | `larr` | Carry of `321xxcolor{red}{8}` |
| | | 3 | 2 | 1 |
| | | × | 7 | 8 |
|
| | 2 | 5 | 6 | 8 | `larr` | `color{red}{321xx8}` |
| 2 | 2 | 4 | 7 | | `larr` | `color{green}{321xx7}` |
|
| 2 | 5 | 0 | 3 | 8 | `larr` | Product |
Multiplication steps
Step-1 : `321xx8=?`
`8xx1=8.``:.` put down `8`
`8xx2=16.``:.` put down `6` and carry `1`
`8xx3=24+1=25.``:.` put down `5` and carry `2` |
Step-2 : `321xx7=?`
`7xx1=7.``:.` put down `7`
`7xx2=14.``:.` put down `4` and carry `1`
`7xx3=21+1=22.``:.` put down `2` and carry `2` |
So, `321xx78=25038`
2. Find `598.5 * 2.3`
Solution:
In 598.5 there are 1 decimal places
In 2.3 there are 1 decimal places
So, total decimal places `=1+1=2`
Ignore the decimal places and multiply the numbers
| | 1 | 1 | 1 | 1 | | `larr` | Carry of `5985xxcolor{green}{2}` |
| | 1 | 2 | 2 | 1 | | `larr` | Carry of `5985xxcolor{red}{3}` |
| | | 5 | 9 | 8 | 5 |
| | | | × | 2 | 3 |
|
| | 1 | 7 | 9 | 5 | 5 | `larr` | `color{red}{5985xx3}` |
| 1 | 1 | 9 | 7 | 0 | | `larr` | `color{green}{5985xx2}` |
|
| 1 | 3 | 7 | 6 | 5 | 5 | `larr` | Product |
Multiplication steps
Step-1 : `5985xx3=?`
`3xx5=15.``:.` put down `5` and carry `1`
`3xx8=24+1=25.``:.` put down `5` and carry `2`
`3xx9=27+2=29.``:.` put down `9` and carry `2`
`3xx5=15+2=17.``:.` put down `7` and carry `1` |
Step-2 : `5985xx2=?`
`2xx5=10.``:.` put down `0` and carry `1`
`2xx8=16+1=17.``:.` put down `7` and carry `1`
`2xx9=18+1=19.``:.` put down `9` and carry `1`
`2xx5=10+1=11.``:.` put down `1` and carry `1` |
Rewrite the answer with 2 decimal places (from the right) = `1376.55`
So, `598.5xx2.3=1376.55`
This material is intended as a summary. Use your textbook for detail explanation.
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