Hard
Complete the number grid by finding the missing value: Row1: 5, 8, 7 | Row2: 11, 17, 15 | Row3: 21, 33, ?
Explanation
Explanation
Each number in row 2 equals double the number above it (in row 1) plus 1: 5x2+1=11, 8x2+1=17, 7x2+1=15. Each number in row 3 equals double the number above it (in row 2) minus 1: 11x2-1=21, 17x2-1=33, and so 15x2-1=29. The missing value is 29.
PRO TIP
Re-check your working by substituting the answer back into the original question.