Proportion percent

Proportion

Percent

Percent means 'per hundred'. 30% means 30/100, or 0.30.

• Write  $33\frac{1}{3}\%$  as a decimal and as a fraction

•  $33\frac{1}{3}\%=\frac{33\frac{1}{3}}{100}=\frac{\frac{100}{3}}{100}=\frac{1}{3}$  

Interest is simple a type of percent increase. Suppose you have taken a loan of $2000 at 8% annual interest. This means that at the end of a year the mount you will owe increase 8% or $160.

• 75 is 20% of what number?

• x * 20% = 75, x = 375

Suppose you borrow $4000 at 5% annual interest. How much money will you owe after 4 years? (you can use calculator)

• after one year, you owe $4000(1.05)

• after two years, you owe $4000(1.05)(1.05)

• ... 4 years, you owe $4000(1.05)^4

• answer is $4862.03

If two liters of a 20% acid solution are mixed with 8 liters of a 50% acid solution, what is the concentration of the resulting solution?

• Concentration=acid/total liquid

• acid = 2 * 20% + 8 * 50%, total liquid = 2+8

• (0.4 + 4)/10 = 44%