The number \( 5.1 \times 10^7 \) in decimal notation can be written by moving the decimal point in \( 5.1 \) seven places to the right.
Starting with \( 5.1 \):
- Moving the decimal one place right gives \( 51. \)
- Moving it two places gives \( 510. \)
- Moving it three places gives \( 5,100. \)
- Moving it four places gives \( 51,000. \)
- Moving it five places gives \( 510,000. \)
- Moving it six places gives \( 5,100,000. \)
- Moving it seven places gives \( 51,000,000. \)
So, \( 5.1 \times 10^7 \) in decimal notation is 51,000,000.