Answer:
29 years
Step-by-step explanation:
In 29 years the grandson will be 40 and the grandfather will be 80. 80 is twice as much as 40.
Answer: 29 years
Step-by-step explanation: if the grandfather is 51 when the grandson is 11 then the grandfather was 40 when his grandson was born. This mean the grandfather will be 80 when the grandson is 40. 40-11=29
