Monthly inflation rate (basic percentage)

Question

The Central Bank's Bulletin, on 07/12/2021, projected inflation for 2021 at 6.11%. If inflation in the months of January to June 2021 were:

January: 0.25%

February: 0.86%

March: 0.93%

April: 0.31%

May: 0.83%

June: 0.53%

What should be the average monthly inflation for the next 6 months, for the Bulletin projection to be correct?

A) 0,367% per month

B) 0,373% per month

C) 0,405% per month

D) 0,421% per month

I did solve this question, but couldn't figure it out as my answer is not exact. I would really really appreciate if you could explain to me how to solve the question, and include the answer

Answer 1

6.11% for the year is the same as 6.11/12 % per month or 611/1200 % per month

To get that average, we add all the months together and divide by 12.

Avg = 611/1200 = [0.25 + 0.86 + 0.93 + 0.31 + 0.83 + 0.53 + (sum of the last 6 months)]/12

Multiply both sides by 12 to get:

(12)(611)/(1200) = [0.25 + 0.86 + 0.93 + 0.31 + 0.83 + 0.53 + (sum of the last 6 months)]

611/100 = 3.71 + (sum of the last 6 months)

6.11 - 3.71 = (sum of the last 6 months)

2.4 = (sum of the last 6 months)

The average for the last 6 months is the sum divided by 6 so:

Avg monthly inflation = 2.4/6 = 0.4%

I see your dilemma. Any other tutors see something I've missed?