GRE Sample Test 4 Quantitative Reasoning 1

In the two-digit number jk, the value of digit j is twice the value of digit k. You have to compare the value of k in Quantity A with 6 in Quantity B. If you plug in 6 for k, it is not possible to enter “twice the value of the digit k” for the digit j. That is because j can only be a single digit; it cannot be 12. In other words, k has to be something less than 6, so the answer must be (B). The value in Quantity B is greater.