Question

5.5 cm rain falls on the sixth day. So the average of rainfall of previous days
increases by 5 mm. Find the total rainfall of six days.

Answer 1

can you re ask the question is the math section.

Answer 2

Given:

Rain fall on sixth day = 5.5 cm =   55 mm      (1cm = 10 mm)

Average of rain fall increase = 5mm

To find :

Total rain fall of 6 days = X mm

Let the average  rain fall of 5 days = y mm

$\textbf{\Large Average of rainfall} = \frac{\textbf{\Large Total quantity of rain fall } }{\textbf{\Large No. of days} }$                                            

                                                                                                    ( 1 )

So, The average rain fall of 6 days

= (y + 5) mm                     (given info.)

Then, by ( 1 ),

Total rain fall in 5 days

= $5\times y$ mm                                            ( 2 )

Total rain fall in 6 days  (X)

=  $6\times (y + 5)$ mm = $6\times y + 30$ mm        ( 3 )

It is given that rainfall on only 6th day = 55 mm

Then for  the value of y

(3 )- (2) = rain on 6th day

So,

$(6\times y + 30) - (5\times y) = 55 mm\\\\y + 30 = 55 mm\\\\So,\\y= 25 mm$

As y = 25 mm found

then by (3)

$\textbf{\Large The total rainfall of six days = 6y + 30 =}( 6\times 25) + 30 = \textbf{\Large 180 mm}$

$\textbf{\Large Solution = 180 mm}$