Uzanne can work 10 math problems in 15 minutes. How many can she work in an hour and a half?

1 and half hour

= 60 minutes + 30 minutes

= 90 minutes

Now,

Uzanne need 15 minutes to do 10 problems

Uzanne need 1 minute to complete 10/15 problems

Uzanne need 90 minutes to do

= (10/15) * 90

= (2/3) * 90

=2*30

=60 problems