Leading digit estimation, did I get these answers right (need to know if I'm doing it correctly)?

1. Use Leading Digit Estimation to estimate the answers to the following problems. a. 8.9 + 5.3 + 14.8 =9.0+5.0+15.0= 29 b. 3139 × 11 =3000x10= 30,000 c. 4122/23 =4000/20= 200 2. Use Leading Digit Estimation to estimate the answers to the following problems. a. 19.2 + 9.3 + 48.9 =19.0+9.0+49.0= 77 b. 93 × 41 =90x40= 3600 c. 2117/17 =2000/20= 100