Kerry walks 3 miles each day. How far will she walk in 7 days?

Hint: Here in this question, we have to find how far Kerry walks in 7 days. This problem is based on the concept of ratio and proportion. Given the how far Kerry walks in each day by using this we can find the required distance which Kerry walks in 7 days. By using the basic arithmetic operation.

Complete step by step solution:
The question is a word question. We read the question and we write the data from the question.
Consider the given data in question
Kerry walks 3 miles in each day or one day this can be written as
Kerry walks in each day = \[\dfrac{{3\,miles}}{{1\,day}}\]
Here, we have to find the how far Kerry walks in 7 days
Let us take
The distance Kerry walks in 7 days = d miles
This can be written as
Kerry walks in seven days = \[\dfrac{{d\,miles}}{{7\,day}}\]
Basically, it is a ratio and proportion problem
Then consider the two ratios and we equate the both ratios and then it is written as
 \[ \Rightarrow \dfrac{{3\,miles}}{{1\,day}} = \dfrac{{d\,miles}}{{7\,day}}\]
On cross multiplication, we have
 \[ \Rightarrow 3 \times 7 = d\]
On multiplication, we get
 \[ \Rightarrow 21 = d\]
Or
 \[ \Rightarrow \,d = 21\] miles
Hence, Kerry walks 21 miles in 7 days.
So, the correct answer is “21 miles ”.

Note: Here in this we use the simple trick. We write the given data and then we use the cross multiplication. Then we use the simple multiplication. While multiplication or multiplying the numbers, we must know the table of multiplication. Hence we determine the result for the given question.