Kathleen projects her expenditures for purchasing office supplies to be $85/week. How much will she spend on office supplies over a 4-week time span?
A)$290
B)$325
C)$340
D)$355
E)$342

Question

Quizplus · Accepted Answer

$340. It is very easy to mentally multiply a number by 4. Simply double the number, then double that resulting number. In this case, 85 doubled is 170, and 170 doubled is 340.
Key Takeaway: This trick of doubling numbers twice in order to multiply by four comes in handy when you are doing calculations related to quarters, for example. This isn't a tough question, but speed is what matters here.

Kathleen Projects Her Expenditures for Purchasing Office Supplies to Be