Hi Ritika,

given in the question are,

Total number of marks = 1000

Marks obtained by A = 720

Percentage of A = (720 / 1000) X 100 = 72%

A/Q, it is 90% of B

So, percentage of B = (72 / 90) X 100 = 80%

It was 125% of C

So, percentage of C = (80 / 125) X 100 = 64%

Now, It was 80% of D

So, percentage of D = (64 / 80) X 100 = 80%

The percentage of marks obtained by D is 80%.

Now If M get x% less than N.
And N get y then we have to find what M gets.
M gets y - y *x/100
So if M gets z then z=y(100-x/100)
y=100z/100-x
So A got 10% less than B
A got 720 then B got =100*720/90=800
B got 25% more than C which is -25% less than C
Then C got =100*800/125=640
C got 20% less than D
Then D got =100*640/80=800
Then D got (800/1000*100 =)80% of the maximum marks