Adding a Fifth Row

The arrangement of the pins for Ten Pins is
at right.
Say that another row of pins were added.
How many pins are in that row?

Row 1 has 1 pin,

Row 2 has 2 pins,

Row 3 has 3 pins,

Row 4 has 4 pins,

Row 5 has ________ pins.

Row 5 will have 5 pins in it.

(Click the image to see the added row.)