Question

The average monthly rainfall in a city in a particular year from january to june was 15 mm and from july to october was 65mm. The rainfall in november and december put together was 34 mm. What was the average monthly rainfall for the entire year in that city?

Answer 1

average monthly rainfall in a city

= 15+65+34/12

=114/12

=9.5

average monthly rainfall if a city are 9.5 mm

Answer 2

Answer: 34.83

Step-by-step explanation:

Formula for Average : $\dfrac{\text{Sum of observations}}{\text{Number of observations}}$

Given : The average monthly rainfall in a city in a particular year from January to June was 15 mm and from July to October was 65 mm.

No. of months from January to June = 6

Let 'a' be the sum of rainfall from from January to June ,  then

$15=\dfrac{a}{6}\\\\\Rightarrow\ a=90$            (1)

No. of months from July to October = 4

Let 'b' be the sum of rainfall from from July to October ,  then

$65=\dfrac{b}{4}\\\\\Rightarrow\ b=260$            (2)

The rainfall in November and December put together was 34 mm.

No. of months from November and December= 2

Let 'c' be the sum of rainfall from from  November and December ,  then

$34=\dfrac{c}{2}\\\\\Rightarrow\ c=68$          (3)

Now, by using (1) , (2) and (3),

The average monthly rainfall for the entire year in that city :-

$\dfrac{a+b+c}{12}=\dfrac{90+260+68}{12}\approx34.83$

Hence, the average monthly rainfall for the entire year in that city was 34.83