.
Lauri and Anže are baking cookies for a village festival. Anže baked 2/3 as many cookies as Lauri.
After the morning rush, Anže had 10 fewer cookies left than the number he had originally baked.
Lauri had 1/4 as many cookies left as Anže. By the end of the day, the difference
between the number of cookies they each had left was 30. How many cookies did Lauri bake at first?
~~~~~~~~~~~~~~~~~~~~~~~~~~~
This problem is good to solve it by the backward method.
Doing this way, the solution to the problem becomes simpler.
Let x be the number of cookies Lauri had left at the end of the day.
Then, according to the problem, Anze had left 4x cookies at the end of the day.
Next, according to the problem,
4x - x = 30, or 3x = 30, which implies x = 30/3 = 10.
So, at the end of the day, Lauri had 10 cookies left, while Anze had 4*10 = 40 cookies left.
Hence, initially Anze did bake 40 + 10 = 50 cookies.
These 50 cookies are 2/3 of the number of cookies that Lauri initially baked.
Hence, Lauri baked initially = 3*25 = 75 cookies.
ANSWER. Lauri did baked 75 cookies at first.
Solved.