Completely depends on the person.
A boy that is 4 foot 9 inch should weigh between 30 to 40 kilograms. This is the ideal weight but it varies in most cases.
152 pounds
100-115
125 lbs
about 75-86 pounds
150-165lbs
117 - 143 lbs.
About 120-133 Pounds
125 to 140
about 170 if muscular. but most people are not so 130? or 140?
well you should weigh at least 80 to 100 pounds