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Puzzle 369
What is the easiest way to make this equation correct?
Hint
It doesn't matter what the distance is, so try a random distance.
Answer
This cannot be done.
It does not matter how far the trip is, let's assume that it is random distance, say 60 miles, and remembering that Time = Distance ÷ Speed.
The morning trip took 60 miles ÷ 30 mph = 2 hours.
To average the required 60 mph, we would have to travel the total distance (of 120 miles) in 2 hours. However, we've already used all of the two hours for the morning trip!
Choosing any random distance would also show that it can't be done.
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Puzzle 371
I recently asked a friend of mine to buy me some ribbon for my latest embroidery project.
He went to the haberdashery shop for a particular length, but he accidentally interchanged the feet and inches.
When I measured the purchased ribbon, I only had 30% of the length I required!
Answer
I asked for 9 foot 2 inches (110 inches) and my friend brought me 2 foot 9 inches (33 inches).
Reasoning
I asked my friend to buy me A feet and B inches, which is a total of 12A + B inches.
He accidentally bought me B feet and A inches, which is 12B + A inches.
We know that 12B + A is actually only 30% of what I wanted, so:
12B + A = 0.3 x (12A + B)
Multiply throughout by 10:
120B + 10A = 3 x (12A + B)
120B + 10A = 36A + 3B
117B = 26A
B = 26A ÷ 117
Don't forget that A and B can only be integers, and between 0 and 11.
Since 26 x A has to be at least 117, the lowest possible value for A is 5. We can check the remaining possibilities.
5 x 26 = 130
6 x 26 = 156
7 x 26 = 182
8 x 26 = 208
9 x 26 = 234 (*)
10 x 26 = 260
11 x 26 = 286
The only number wholly divisible by 117 is 234, which means that A = 9, and B = 2.
So, I originally asked for 9 feet 2 inches.
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Puzzle 372
Can you find a three-digit number such that when you reverse the numbers you get a larger number and the product of these two numbers is 224455?