Question

a 3500
3. The average of Suresh's marks in English and History is 55. His average of marks in English and Science is 65.
the difference between the marks which he obtained in History and Science?​

Answer 1

Answer:

20

Step-by-step explanation:

let mark in history be h

mark in science be s

mark in english be e

then h+e/ 2= 55

h+e=110

e=110-h

s+e=130

substituting value of e in s+e=130

s+110-e=130

s-e=130-110

s-e=20

Answer 2

The difference between the mark obtained in History and Science (H - S) is - 20.

The average of Suresh's marks in English and History is 55. His average of marks in English and Science is 65.

We have to find the difference between the marks which he obtained in History and Science.

we know,

average is the ratio of the sum of observations to the number of observations.

Let mark obtained in English , History and Science are E , H and S respectively.

∴ average mark of English and History = (E + H)/2

⇒55 × 2 = E + H

⇒E + H = 110 ...(1)

similarly,

average mark of History and Science = (E + S)/2

⇒65 × 2 = E + S

⇒E + S = 130 ...(2)

from equations (1) and (2) we get,

equation (2) - equation (1)

⇒(E + H) - (E + S) = 110 - 130

⇒H - S = - 20

Therefore the difference between the mark obtained in History and Science (H - S) is - 20.