Question

The average of first three numbers among four given numbers is 15 and
the average of last three numbers is 16. If the last number is 19 then what
is the first number?
(a) 16
(b) 18
(c) 20
(d) 17​

Answer 1

Answer :

Step-by-step explanation :

➡️ average of first 3 =15

sum of 1st 3 no. = 3×15=45

& also,

➡️ last 3 no. =16

sum of last 3 =16×3=48

in it,

➡️ last no is 19

so middle two =48-19=29

so 29 minus from first 3

so 1st no =45 -29

1st no. =16

so,

let 2nd no be x and 3rd be 29 - x

according to the 1st conditions

=> 16 +x+29 -x =45

=> x + 29 - x = 29

let x be 15

so 3rd no be 14 ans.