Asnwer: average atomic mass of chromium is 52amu
Calculations:
49.946amu: 4.350%= 0.0435
51.941amu: 83.790%= 0.8379
52.941amu: 9.500%= 0.095
53.939amu: 2.360%= 0.0236
Average atomic mass of chromium = 0.0435(49.946) + 0.8379(51.941) + 0.095(52.941) + 0.0236(53.939)
= 51.9963703amu
= 52 amu