Find the sum. \( \sum_{i=1}^{5} 7 i=\square \)

To calculate the sum \( \sum_{i=1}^{5} 7i \), we can first factor out the 7: \[ \sum_{i=1}^{5} 7i = 7 \sum_{i=1}^{5} i \] Now we need to calculate \( \sum_{i=1}^{5} i \), which is the sum of the first 5 natural numbers: \[ \sum_{i=1}^{5} i = 1 + 2 + 3 + 4 + 5 = 15 \] Now, substituting this value back into the equation: \[ 7 \sum_{i=1}^{5} i = 7 \times 15 = 105 \] So the sum is \( 105 \). Therefore, \( \sum_{i=1}^{5} 7 i = \square 105 \).