Question 165376
let x be the original value of the 1st question so you 
start with x and then double the value of each next question so the 2nd question would be worth 2x, the third would be 2(2x)=4x, the 4th worth 2(4x)=8x and the 5th worth 2(8x)=16x.   so if the 5th question is worth 6400 and it took 16 time the original value to get there, then  16x=6400 solving for x the original value we get $400

answer: $400