Question

Find the sum of the odd numbers between 11 and 199 inclusive ​

Answer 1

Answer:

The sum of the odd numbers between 11 and 199 inclusive

= 9,975

Step-by-step explanation:

Old numbers between 11 and 199 are:

11 13 15 17 19 21     23 25 27 29 = 200

31 33 35 37 39 41     43 45 47 49 = 400

51 53 55 57 59 61     63 65 67 69 = 600

71 73 75 77 79 81     83 85 87 89 = 800

91 93 95 97 99 101   103 105 107 109 = 1,000

111 113 115 117 119 121   123 125 127 129 = 1,200

131 133 135 137 139 141    143 145 147 149 = 1,400

151 153 155 157 159 161    163 165 167 169 = 1,600

171 173 175 177 179 181    183 185 187 189 = 1,800

191 193 195 197 199  = 975

Total sum = 9,975

Classify the odd numbers into 10 columns, then add each row.  Start by adding the first row, which equals 200.  Each successive row of the old numbers will equal 200 more than the previous row sum.  At the end, add all the row sums to get the sum of the old numbers from 11 to 199.