The average of four numbers is 40. If the first number is one-third of the sum of the remaining numbers, then the first number is:

40

Average of four numbers = 40

Sum of 4 numbers = 40 x 4 = 160

Let first number = A

According to question ,

A = \(\frac{1}{3}\) x Sum of last three numbers 

\(\frac{1}{3}\) x Sum of last three numbers  + Sum of last three numbers = 160

\(\frac{4}{3}\) x Sum of last three numbers  = 160

Sum of last three numbers = 120

So, First number = \(\frac{1}{3}\) x  120

= 40