Thinking skills assessment test

[ponjavic]

So I'm trying out the test to prepare me for my upcoming cambridge interview, there is one problem I can't understand though this one:

44 Sally is helping her father dig worms for fishing.
"That's exactly enough," he says as she places a worm in his tin.
"How many do you need?" she enquires.
"I use 4 worms on my hook and reckon on having to replace an average of one of these
each time I cast. I cast 12 times an hour. Today I will fish 5 pools spending an hour at
the first 4 and an hour and a half at the fifth. I always discard the worms on my hook
when walking between pools."
How many worms are in the tin?
A 66
B 69
C 81
D 86
E 264

I reckon it is D since:
He passes five pools thus 4*5 worms should be placed on the hook.
He spends a total of 5.5 hours at the pools netting 12*5.5=66 throws --> 66 worms.
66+20=86 worms

It is possible that they mean an hour total on the first four pools in this case:
Passes five pools = 20.
spends 2.5 hours casting = 12*2.5=30 casts --> 30 worms.
20+30=50 worms.

According to the answer sheet the answer is C. It should have something to do with 5 pools since 86-5=81 but what?

 

[cdhotfire]

It seems rather simple to me but here I go, well the awnser is 81 because the first cast he does not have to change the worm, so that's actually 11 replaced worms he does in an hour, and 17 on an hour and a half. So 4worms*5pools=20, 11replacedworms*4pools=44, 17replaced worms for the last pool, and then 44+17+20=81.
hope you understood me.

 

[ponjavic]

yep that was where i gained the other five, that's a mean question then, hope I can keep my nerves together at the test

 

[cdhotfire]

Lets hope so, just think problems 2 times in these kinds of things, they usually try to trick you.