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.
?
Puzzle 19
By changing the second letter of each of the words below, can you make another valid word?
You have to change each word such that the second letters will reveal a ten-letter word when read downwards.
Therefore, what now reads 'craihruane' will be a real word. iconcrewfarmoilychoparidfundwaitgnattear
During an exciting weekend of paintball, four friends were having great fun.
The paintballs came in blue, green, yellow and red.
Coincidentally, the four friends had T-shirts in those same colours.
Billie used blue paintballs. The person in the green T-shirt used yellow paintballs. Charlie was not wearing a red T-shirt. Drew used green paintballs and wore a blue T-shirt. Alex was the only person who used paint which was the same colour as their T-shirt.
Can you tell which colour paint they each used and the colour of their respective T-shirts?
Hint
Start by using clues (1) and (4), and then look at clues (5) and (2) to find who wore the green T-shirt.
Answer Wore Paint
Alex red red
Billie yellow blue
Charlie green yellow
Drew blue green
Reasoning
By (1), Billie used Blue paintballs: Wore Paint
Alex
Billie blue
Charlie
Drew
By (4), Drew used Green paintballs and wore a Blue T-shirt: Wore Paint
Alex
Billie blue
Charlie
Drew blue green
By (5), Alex was the only person who used paint that was the same colour as their T-shirt, which means by (2) that Charlie wore the Green T-shirt and used Yellow paintballs: Wore Paint
Alex
Billie blue
Charlie green yellow
Drew blue green
This leaves Alex with the Red paintballs, and by (1), the Red T-shirt. Wore Paint
Alex red red
Billie blue
Charlie green yellow
Drew blue green
Leaving Billie wearing Yellow. Wore Paint
Alex red red
Billie yellow blue
Charlie green yellow
Drew blue green
