At my local farmer's merchant, you can buy chicken feed for 15c per tonne, pig feed for $1.25 per tonne, and cattle feed for 40c per tonne. The feed can only be purchased by the tonne, and part tonnes aren't sold.
Last week I bought some animal feed, and luckily I managed to buy exactly 100 tonnes for exactly $100. How much of each feed did I buy?
Hint
What are the maximum and minimum tonnes of pig feed I could have bought?
Answer
I bought 15 tonnes of chicken feed, 75 tonnes of pig feed, and 10 tonnes of cattle feed.
15 x 0.15 = 2.25 75 x 1.25 = 93.75 10 x 0.40 = 4.00
100 tonnes = $100.00
A possible solution method follows …
I couldn't have bought 80 tonnes of pig feed because this would have cost the full $100.00, but I wouldn't have then had 100 tonnes in total.
Similarly, 70 tonnes of pig feed would have been too few, as this would cost $87.50 and even the remaining 30 tonnes all being cattle feed wouldn't have reached the required $100.00.
So, let's try 71 tonnes of pig feed = $88.75:
plus 1 x chicken feed + 28 x cattle feed is over $100.00 or 2 x chicken feed + 27 x cattle feed is under $100.00
so 71 tonnes of pig feed doesn't work.
Let's try 72 tonnes … and so on.
We soon get to 75 tonnes of pig feed and find the answer.
??
Puzzle 16
Our local scrap merchant had to travel to the county recycling plant, 60 miles away.
On the way there, the wagon was fully laden, so could only manage a steady 12mph.
On the way back, the wagon was much lighter and could manage a steady 16mph.
The wagon started with 24 gallons of fuel in the tank ready for the round trip, which was easily enough fuel as the wagon managed to travel 8 miles for each gallon.
Unfortunately, a piece of metal had pierced the fuel pipe at the very start of the trip, and the wagon began to lose 1 gallon of fuel every hour.
Luckily, it only lost fuel when moving and lost no fuel while unloading the scrap metal.
Were the 24 gallons enough for the entire round trip?
