Answer:
120
Explanation:
So 10% of a number (let's use n) is 30.
The key word "of" tells us we need to multiply. Therefore, 10% times n is 30:
![10\%(n)=30](https://img.qammunity.org/2021/formulas/mathematics/high-school/8s4g1783smf4l8bcot39rqsoppk66o3s1t.png)
10% is the same as 0.1. So:
![0.1n=30](https://img.qammunity.org/2021/formulas/mathematics/high-school/ymjt4hciak42b690c9ziu34evu6533zd13.png)
Divide both sides by 0.1:
![n=300](https://img.qammunity.org/2021/formulas/mathematics/high-school/tpi28t5npkzluur16y5oxb874l4kj22bnf.png)
So, our number is 300.
To find 40% of 300, multiply 0.4 and 300. Thus:
![.4(300)=120](https://img.qammunity.org/2021/formulas/mathematics/high-school/vdpears4i73oowmwyudl05kh37vyhvbp2t.png)
Our answer is 120.
And we're done!