The arithmetic mean of 3 numbers is 17. removed one of these numbers, the arithmetic mean of the remaining two numbers is 18. which number has been removed.
1. Let’s designate three numbers as х, y, с.
2. Let’s compose an expression for finding the arithmetic mean of three numbers.
(x + y + c): 3 = 17
3. Let’s compose an expression for finding the arithmetic mean of two numbers.
(x + y): 2 = 18
x + y = 18 * 2
x + y = 36
3. Substitute the found sum of two numbers into the expression for finding the arithmetic mean of three numbers.
(36 + с): 3 = 17
36 + c = 17 * 3
36 + c = 51
с= 51 – 36
c = 15
Answer: removed the number 15.
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