The numeral 1101101 is written in base two. What is its value in base ten?

The place values from the left are 64, 32, 16, 8, 4, 2, 1. The digits 1, 1, 0, 1, 1, 0, 1 therefore give 64 + 32 + 0 + 8 + 4 + 0 + 1 = 109. Reading the digits from the wrong end (1011011) gives 64 + 16 + 8 + 2 + 1 = 91, which is the most common slip here.