Four More Math Puzzles
Here are a few more math puzzles to exercise that brain.
1. Look at the following:
1 + 23 - 4 + 5 - 6 + 78 + 9 = 106
Notice that the digits 1 through 9 are used in order to arrive
at 106. Using 1 through 9 in order, and using only addition or
subtraction, create an equation that equals 100.
2. Mary is 54 years old, and
her mother is 80. How many years ago was her mother three times
the age of her daughter Mary?
3. John needed some small bills
because he was traveling. He went into a bank and gave the teller
a $100 bill. He told her, "I need some two-dollar bills,
ten times as many one-dollar bills, and the rest in five-dollar
bills. How many of each did the teller give him?
4. Bob makes and sells picnic
tables from his yard for $100 each. His only costs are for materials.
It takes him an hour and half to make a table. He sold 200 last
year, for a profit of $3,000. This year he raises the price by
15%, but sells 30% fewer tables. Assuming his cost for making
each table hasn't changed, by what percentage does his profit
increase?
Solutions
1. 12+3-4+5+67+8+9 = 100. But that's just one solution.
"Fuzz" sent me this one: 123+45-67+8-9 = 100.) Here
are some Vipul sent (thank you):
1+2+3-4+5+6+78+9=100
1+2+34-5+67-8+9=100
1+23-4+5+6+78-9=100
1+23-4+56+7+8+9=100
12+3+4+5-6-7+89=100
12-3-4+5-6+7+89=100
123+4-5+67-89=100
123-4-5-6-7+8-9=100
123-45-67+89=100
2. 41 years ago, when Mary was 13 and her mother was
39.
3. He was given five two-dollar bills, fifty one-dollar
bills, and eight five-dollar bills, totaling $100.
4. 40%. This is a good business math puzzle, with a
lesson or two in it. His profit on 200 tables was $3,000, or
$15 per table, so we can deduce that his cost is $85 per table.
At the new price of $115 (15% more) he makes $30 per table. Thus,
even though he sells only 140 tables (30% fewer), he makes $4,200
- 40% more than the previous year.
Interestingly, a 15% price increase makes his profit per-hour-of-labor
go up 100%, from $10 per hour to $20 per hour - showing the importance
of selecting the right price.
Note: You can find more on the page: Math
Puzzles.
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