Bunuel
When a positive integer x is divided by d, the remainder is 241 and when 2x is divided by d, the remainder is 112. What is the value of the d ?
A. 129
B. 258
C. 353
D. 370
E. 706
"when a pos. integer x is divided by divisor d, the remainder is 241"
given: (x / d) = Q + (241 / d)
or, the positive integer x can be written as:
x = d(Q) + 241
Property: the remainder must always be less than the divisor
so, divisor d > 241 ---- (we can eliminate answer (A) because it is too small)
"when 2x is divided by d, the remainder is 112"
when we DOUBLE the positive integer x, we are doubling the representation of the value.
let X = the same value represented as X number of balls that we have on the floor
originally, we were able to take X and apportion the balls into Q-quotient groups of D.
however, there were 241 balls left over that could not be made into a group of D balls.
if we take that same picture and DOUBLE it, we will have 241 and 241 balls from each that we were unable to make into a group of D balls.
however, we are told the remainder is 112.
this means we were able to take these (241 + 241 = 482 balls) and make Another group of D balls, with 112 left over.
this also tells us that Divisor - D must be less than < 482 ----we can eliminate answer (E) right away
we can take these 482 balls, divide them into one D group, and have a remainder of 112:
482 = D(1) + 112
D = 370
answer (D)