The average of 13 numbers is 40. The average of the first 7 numbers is 42 and of the last seven numbers is 35. Find the marks obtained in the 7th number.
Answers
Answer:
19
Step-by-step explanation:
Average(13 papers)= 40
(m1+m2+..+m13)/13=40
m1+m2+..+m13=520
Now, According to question:-
Average(first 7 papers)= 42= (m1+m2+….m7)/7
Average(last 7 papers)=35=(m7+m8+..+m13)/7
Average(first 7 paper)+Average(last 7paper)=42+35
(m1+m2+.m7)/7+(m7+m8+..+m13)/7=77
(m1+m2+…m7+m7+m8+..+m13)=77×7
Here you can see marks of 7th subject are coming 2times in addition. So, we can write the above equation as:-
(m1+m2+…+m7+....+m13)+m7=77×7
m7=539–520
m7=19
so marks obtained in 7th paper is 19.
Answer:
The mark obtained in the 7th number is 19.
Step-by-step explanation:
The average marks of 13 subjects are 13×40 = 520
the marks of the 7th paper are x7
and the total marks of the first 6 papers are?
X + x7 / 7 = 42
X+ x7 = 42×7
X + x7 = 294
the marks of the last 6 papers are?
x7 + Z / 7 = 35
x7 + Z = 35×7
x7 + Z = 245
X + Z + 2x7 = 294 + 245 = 539 is equation 1
13 papers are 520
also includes the 7th paper now
if we subtract the actual average from the equation (I) which after calculation contains the marks of two 7th papers then we get the marks of one 7th paper only
therefore the mark of the 7th paper is
539 - 520 = 19