To find out how many ushers are needed when there are 1,050 spectators, we can set up a proportion based on the given information.
We know that:
- When there are 510 spectators, there are 17 ushers.
We can express this as a ratio:
\[ \frac{17 \text{ ushers}}{510 \text{ spectators}} \]
Now, let \( x \) be the number of ushers needed for 1,050 spectators. The proportion then becomes:
\[ \frac{17 \text{ ushers}}{510 \text{ spectators}} = \frac{x \text{ ushers}}{1050 \text{ spectators}} \]
Now, we can cross-multiply to solve for \( x \):
\[ 17 \times 1050 = 510 \times x \]
Calculating \( 17 \times 1050 \):
\[ 17850 = 510x \]
Now, solve for \( x \):
\[ x = \frac{17850}{510} \] \[ x = 35 \]
So, if there are 1,050 spectators, then 35 ushers are needed.
Therefore, the answer is 35 ushers.