Excel giving incorrect answer to simple multiplication

HelloBrettDes​, 

This behavior is caused by Excel’s use of binary floating-point arithmetic, not a calculation bug. Excel stores numbers using the IEEE 754 standard, and many decimal fractions like 0.01 cannot be represented exactly in binary. Each time you multiply by 2, the tiny approximation error doubles. By day 49–51, this accumulated error affects the last cent, which is why you see .20 instead of .24 and .50 instead of .48. Formatting as Currency only changes the display, not the stored value. Microsoft documents this here: https://learn.microsoft.com/office/troubleshoot/excel/floating-point-arithmetic-inaccurate-result. To avoid this, either work in whole integers (e.g., cents) and convert to dollars for display or round at each step using =ROUND(A1*2,2). Either approach prevents cumulative rounding errors.