Subtract 0.5
238
minus one half
two and one half
If it is a diameter then you must be in a cylinder or domed room. To get the thickness take the external and subtract the internal then divide the result in half.
The wording is ambiguous. If the questions means, "From what number can you subtract one-half to get a result of zero?" then the answer is one-half. (1/2) - (1/2) = 0 If the question means, "From what number can you subtract half of the number to get a result of zero?" then the answer is zero. 0 - (1/2)0 = 0
Subtract 0.5
half the result
...but if you multiply a whole number by a half the result decreases. Half of anything is less than that thing!
238
minus one half
1.25
34?
Well, split 70 in half: 35 + 35. Add 4 (half of the 8) to one half: 39. Subtract 4 (the other half of 8) from the other half: 31. The smaller number is 31.
Subtract the difference and half your answer, giving 9 which is the smaller number, add the difference to this and you get 38 which is the larger number.
12
It is 1/6.