Question 1100170
 first AP 2,5,8,11....to 60 terms
2 5 8 11 14 17 20 23 26 29 32 35 38 41 44 47 50 53 56 59 62 65 68 71 74 77 80 83 86 89 92 95 98 101 104 107 110 113 116 119 122 125 128 131 134 137 140 143 146 149 152 155 158 161 164 167 170 173 176 179 ct 60
second AP 3,5,7...50 terms
3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 55 57 59 61 63 65 67 69 71 73 75 77 79 81 83 85 87 89 91 93 95 97 99 101 ct 50
Notice that the second AP are all the odd numbers 3 to 101
So just count the odd numbers in the first AP.

This a method of solution. It is not a solution based on equations and formulas but as Ikleyn often says based on logic. It is certainly an easier method. All you have to do is look for odd numbers