Question

There are three galleries in a coal mine. On the first
day, two galleries are operative and after some time,
the third gallery is made operative. With this, the
output of the mine became half as large again. What
is the capacity of the second gallery as a percentage
of the first, if it is given that a four-month output of
the first and the third galleries was the same as the
annual output of the second gallery?​

Answer 1

Answer:

Which book does th8s question belong to????