Question

The average of 11 results is 30 that of the
first 5 is 25 and that of the last 5 is 28. The
value of the 6th number is​

Answer 1

Answer:

hope it will help you

Step-by-step explanation:

Let the 11 results be a,b,c,d,e,f,g,h,i,j,k

>>...the average of 11 results is 30,...<<

%28a%2Bb%2Bc%2Bd%2Be%2Bf%2Bg%2Bh%2Bi%2Bj%2Bk%29%2F11%22%22=%22%2230

Multiply both sides by 11

a+b+c+d+e+f+g+h+i+j+k = 330

>>...that of the first five is 25,...<<

%28a%2Bb%2Bc%2Bd%2Be%29%2F5%22%22=%22%2225

Multiply both sides by 5

a+b+c+d+e = 125

>>...and that of the last five is 28...<<

%28g%2Bh%2Bi%2Bj%2Bk%29%2F5%22%22=%22%2228

Multiply both sides by 11

g+h+i+j+k = 140

So we have these three equations:

a+b+c+d+e+f+g+h+i+j+k = 330

a+b+c+d+e = 125

g+h+i+j+k = 140

Subtract the 2nd equation from the 1st:

f+g+h+i+j+k = 205

Subtract the third equation from that

f+g+h+i+j+k = 205

g+h+i+j+k = 140

f = 65

Answer 65.