What is answer

Question

Dennis thought of a number. He adds 0.5 to that number and then multiplies the new result by 4. He then subtracts 2 and divides the number by 2. His final answer is 48. What number did Dennis start with?

Answer 1

Let’s call the number n and track what happens to it.

(4(n+0.5)-2)/2=48 is the mathematical expression of the words. Start in the innermost brackets and work outwards. To find the answer we reverse all the operations:

Multiply the outcome by 2: 2×48=96 because the last operation was division, so the first operation in the solution is multiplication. Now we have 4(n+0.5)-2=96. Last operation was subtract 2 so we add 2 to 96 to get 98. That gives us 4(n+0.5)=98. Now divide 98 by 4=24.5. So n+0.5=24.5. Subtract 0.5 and we get n, the number=24.