Mamma: "Let me think, Tommy. Well, our three ages add up to exactly seventy years."
Tommy: "That's a lot, isn't it? And how old are you, papa?"
Papa: "Just six times as old as you, my son."
Tommy: "Shall I ever be half as old as you, papa?"
Papa: "Yes, Tommy; and when that happens our three ages will add up to exactly twice as much as to-day."
Tommy: "And supposing I was born before you, papa; and supposing mamma had forgot all about it, and hadn't been at home when I came; and supposing--"
Mamma: "Supposing, Tommy, we talk about bed. Come along, darling. You'll have a headache."
Now, if Tommy had been some years older he might have calculated the exact ages of his parents from the information they had given him. Can you find out the exact age of mamma?
Mamma's Age, Amusements In Mathematics, Henry Ernest Dudeney.
Hint
The answer isn't a whole number of years, and algebra might be required.
Answer
29 years 2 months.
Reasoning #1
This answer is taken directly from the original book.
The age of Mamma must have been 29 years 2 months; that of Papa, 35 years; and that of the child, Tommy, 5 years 10 months. Added together, these make seventy years. The father is six times the age of the son, and, after 23 years 4 months have elapsed, their united ages will amount to 140 years, and Tommy will be just half the age of his father.
Reasoning #2
Here's my answer, with a little algebra.
If we call Tommy T, Mamma M and Papa P we can see that:
"our three ages add up to exactly seventy years" gives us:
(1) T + M + P = 70
"Just six times as old as you" gives us:
(2) P = 6 x T
In an unknown number of years (Y) "Shall I ever be half as old as you" gives us:
(3) P + Y = 2 x (T + Y)
and "our three ages will add up to exactly twice as much as today" gives us:
(T + Y) + (M + Y) + (P + Y) = 140
which can be written as
(4) T + M + P + 3Y = 140
We can see from (4) and (1) that
3Y = 70
so
(5) Y = 70 ÷ 3
Using (2) and (5) in (3) we have
P + Y = 2 x (T + Y)
6 x T + 70 ÷ 3 = 2 x (T + 70 ÷ 3)
4 x T = 70 ÷ 3
(6) T = 70 ÷ 12
We can now use (6) in (2) to see that:
P = 6 x T
P = 6 x 70 ÷ 12
P = 70 ÷ 2
And using the values for T and P in (1) we have:
T + M + P = 70
70 ÷ 12 + M + 70 ÷ 2 = 70
Multiply throughout by 12 to give:
70 + 12 x M + 420 = 840
12 x M = 840 – 420 – 70
12 x M = 350
M = 350 ÷ 12
So:
Tommy = 70 ÷ 12 = 5.83333 = 5 years 10 months. Papa = 70 ÷ 2 = 35 = 35 years. Mamma = 350 ÷ 12 = 29.1666 = 29 years 2 months.
You find yourself playing a game with your friend.
It is played with a deck of only 16 cards, divided into 4 suits:
Red, Blue, Orange, and Green.
There are four cards in each suit:
Ace, King, Queen, and Jack.
All Aces outrank all Kings, which outrank all Queens, which outrank all Jacks, except for the Green Jack, which outranks every other card.
If two cards have the same face value, then Red outranks Blue, which outranks Orange, which outranks Green, again except for the Green Jack, which outranks everything.
Here's how the game is played: you are dealt one card face up, and your friend is dealt one card face down. Your friend then makes some true statements, and you have to work out who has the higher card, you or your friend. It's that simple!
Round 1:
You are dealt the Green Ace and your friend makes three statements:
My card is higher than any Queen. Knowing this, if my card is more likely to beat yours, then my card is Blue. Otherwise, it isn't. Given all of the information you now know, if your card is more likely to beat mine, then my card is a King. Otherwise, it isn't.
Who has the higher card, you or your friend?
Hint
List all of the cards, and then eliminate some using (1).
Answer
Your friend.
Reasoning
You were dealt the Green Ace.
The possible cards, in order, are:
Green Jack
Red Ace
Blue Ace
Orange Ace
Green Ace (your card)
Red King
Blue King
Orange King
Green King
Red Queen
Blue Queen
Orange Queen
Green Queen
Red Jack
Blue Jack
Orange Jack
By (1), your friend's card is higher than any Queen, so your friend can only have one of these cards:
Green Jack
Red Ace
Blue Ace
Orange Ace
Green Ace (your card)
Red King
Blue King
Orange King
Green King
By (2), their card is not more likely to beat yours (4 v 4), so their card is not Blue, leaving:
Green Jack
Red Ace
Orange Ace
Green Ace (your card)
Red King
Orange King
Green King
By (3), your card is not more likely to beat theirs (3 v 3), so your friend's card is not a King, leaving:
Green Jack
Red Ace
Orange Ace
Green Ace (your card)
At the recent BrainBashers downhill mountain bike race, four entrants entered the challenging slalom event.
Alex finished in first position. The entrant wearing number #2 wore red, but Drew didn't wear yellow. The person in last place wore blue, and Stevie wore number #1. Glen beat Stevie, and the person who finished in second wore number #3. The entrant in yellow beat the entrant in green. Only one of the entrants wore the same number as their final position.
Can you determine who finished where, the number, and colour they each wore?
Hint
Start by looking at where Alex finished, and where the person who wore #3 finished, and then use clue (6).
Answer Pos Name Wore Colour
1 Alex #2 red
2 Glen #3 yellow
3 Stevie #1 green
4 Drew #4 blue
Reasoning
The four colours were: blue, green, red, yellow.
The four contestants were: Alex, Drew, Glen, Stevie.
By (1), Alex was first.
1 Alex
2
3
4
By (4), the person who was second wore number #3.
1 Alex
2 #3
3
4
Looking at (6):
- first place (Alex) can't have worn #1, because, by (3), Stevie wore #1
- second place wore #3
- third place can't have worn #3, because it was worn by second place
- fourth place is the only entrant who could have worn the same number as their final position
Therefore, Stevie finished in third, and Alex wore #2.
1 Alex #2
2 #3
3 Stevie #1
4 #4
By (2), Alex wore red. By (3), the person wearing blue was last.
1 Alex #2 red
2 #3
3 Stevie #1
4 #4 blue
By (5), yellow beat green.
1 Alex #2 red
2 #3 yellow
3 Stevie #1 green
4 #4 blue
By (4), Glen beat Stevie.
1 Alex #2 red
2 Glen #3 yellow
3 Stevie #1 green
4 #4 blue
Leaving Drew in last place.
1 Alex #2 red
2 Glen #3 yellow
3 Stevie #1 green
4 Drew #4 blue
Note: BrainBashers has a Dark Mode option. For BrainBashers, I'd recommend not using your browser's built-in dark mode, or any dark mode extensions (sometimes you can add an exception for a specific website).
