Rate of interest is 6 %
<em><u>Solution:</u></em>
Given in question that,
simple interest = $ 3240
number of years = 9 years
principal sum = $ 6000
To find: interest rate
<em><u>The simple interest is given as:</u></em>

Where, "p" is the principal
"r" is the rate of interest
"n" is the number of years
<em><u>Substituting the values in above formula,</u></em>

Thus rate of interest is 6 %
For this you need to use the reverse cosine function
Cos^-1 (.25)
75.6
Answer:
39
Step-by-step explanation:
84 words = 2 min
1 word = 2/84 = 1/42
420 words = 1/42 x 420 = 10 mins
Answer: 10 mins