Conversion of weekly rent to monthly

Ebb422

Hey everyone, apologies if I make any mistakes here, I don't really spend any time here. I'm moving into student accommodation with 3 other people and our rent is accrued weekly but paid monthly, it is £90 per week and we all have varying contract lengths. 
What confuses me is that we're all paying different monthly amounts even though our weekly payments are the same, the justification given for this by the landlord is shown below. 

My view was that considering we're each paying the same weekly amount, we should also be paying the same monthly amount, which if you use the formula Monthly Payments = ((90/7) x 365.25)/12 should be £391.34 per month. The only difference is how long we pay that amount for.
I would really just like this all confirmed because it seems very strange. 
Thank you.
Below is the tenancy agreement:
 

MaryNB

The ratios between the weeks and months are different.

J is paying 4.33 weeks' worth of rent per month
T is paying 4.45 weeks' worth of rent per month
R is paying 4.10 weeks' worth of rent per month
A is paying 4.00 weeks' worth of rent per month

The amount of weeks each is renting does not line up exactly with the number of months they are paying rent and the relationship between the two is different per person.

ETA: sorry, still trying to work out how best to explain it.
T for example owes 
£90 x 41 = £4,410
Landlord has done it so T pays the same amount every month.

Your ways means that T pays
£391.34 x 11 = 4,307.74 for 11 months and then £102.26 for the last month. 

Landlord has just distributed the payments equally across all the applicable months. Your method involves some pro rata payments. 

  

Ebb422

MaryNB said:

The ratios between the weeks and months are different.

J is paying 4.33 weeks' worth of rent per month
T is paying 4.45 weeks' worth of rent per month
R is paying 4.10 weeks' worth of rent per month
A is paying 4.00 weeks' worth of rent per month

The amount of weeks each is renting does not line up exactly with the number of months they are paying rent and the relationship between the two is different per person.

ETA: sorry, still trying to work out how best to explain it.
T for example owes 
£90 x 41 = £4,410
Landlord has done it so T pays the same amount every month.

Your ways means that T pays
£391.34 x 11 = 4,307.74 for 11 months and then £102.26 for the last month. 

Landlord has just distributed the payments equally across all the applicable months. Your method involves some pro rata payments. 

  

That's great, thank you for the explanation!