Deficit from June 11 to June 15 = 350 X 5
Deficit from June 16 to June 20 = (350+500) X 5 = 850 X5
Total Deficit = 1200 X 5 = 6000
That means, for the remaining 10 days, the excess (over 1000) must be 600 (6000/10), so the daily balance needs to be 1600. But on June 20, we already have a balance of 150 (1000-350-500), so we need to deposit 1450 (1600-150) to reach 1600 for the next 10 days and a daily average of 1000 for the month.
anon1

For a certain savings account, the table shows the three transactions for the month of June. The daily balance for the account was recorded at the end of each of the 30 days in June. If the daily balance was $1,000 on June 1 and if the average (arithmetic mean) of the daily balances for June was $1,000, what was the amount of the deposit on June 21?
A. $1,000
B. $1,150
C. $1,200
D. $1,450
E. $1,600
Attachment:
Untitled.png
Okay, so june 1 - june 10, the sum of the daily balance in this time period here is 10,000 (because initial balance is 1000, and nothing changes)
june 11-15 - the sum here is 3250 (1000-350)*5
june 15-20 the sum here is 750 (1000-350-500)*5
the sum of all those is 14,000.
Since we want to find a deposit, whose sum makes the total sum of all the balances 30,000 / 30 = 1,000
I did 30,000 - 14,000 which gives me 16,000.
so the sum of the balances for rest of the days (10) must equal 16,000. I do 16,000/10
and that's 1,600. E. But thats wrong. The answer is D
What am I donig wrong here? and what is the false logic?
Solving this question helps.
Taking a timed set of similar questions in
GMAT Club Forum Quiz →
is even better.