[UF150] Half as Old

Half as Old (Sisterly Sums in the UK version) is a puzzle in Professor Layton and the Unwound Future.

Puzzle

US Version

Two sisters are talking about their ages:

"One year ago, I was exactly half as old as you," said the younger one.

The older sister replies: "Even one year from now, your age will be half my age. Here, look, if we split the numbers into two parts, top and bottom, they both give your age in a year's time."

"Hey, you're right. That's really cool!"

How old is the little sister?

UK Version

Two sisters are talking.
"One year ago, my age was exactly half your age", says the younger sister. The older sister replies: "Even one year from now, your age will be half my age. Here, look, if we split the numbers into two parts, top and bottom, they both give your age in a year's time."
"Wow, you're right!"

How old is the younger sister now?

Hints

Click a Tab to reveal the Hint.

Don't worry about their ages one year ago. The key is what their ages will be one year from now.

Think about what it means to divide a number into a top and bottom half.

Have you figured out what it means to split the numbers into two parts, top and bottom?

From zero to nine, the only numbers that retain a numerical meaning even when they're cut in half are one and eight.

If one year from now the older sister is one year old, the younger sister will also be one, so this can't be right.

If a year from now the older sister is eight years old, the younger sister will be zero, so this also can't be right.

It also doesn't work for 81 or 88...

From Hint Three, you learned that one year from now the older sister will have to be either 11 or 18.

If she's 11, when you divide an 11 into a top and bottom half, you still get 11, so this doesn't work. The only option left is the older sister being 18 one year from now.

Now all you have to do is figure out the little sister's current age.

Solution

Incorrect

Too bad!

Are you overanalyzing it? Try thinking about it from a different perspective.

Correct

US Version

Correct!

The little sister is nine years old.

The older sister is 17. A year ago, the older sister was 16 and the younger was eight, so she was half the age of the older one.

A year from now, the older sister will be 18 and the younger one 10. If you divide an 18 into a top half and a bottom half, each one is a 10!

UK Version

That's right!

The younger sister is currently 9 and the older sister is 17.

One year ago, the older ister was 16 and the younger sister was 8, half her sister's age. One year from now, the older sister will be 18 and the younger sister will be 10. Splitting 18 horizontally gives you 10 twice.

A big thanks to http://professorlayton3walkthrough.blogspot.com

v · d · ePuzzles in Professor Layton and the Unwound Future

Normal	001 002 003 004 005 006 007 008 009 010 011 012 013 014 UK 015 016 017 018 019 020 021 022 023 024 025 026 027 028 029 030 031 032 033 034 035 036 037 038 039 040 041 042 043 044 045 046 047 048 049 050 051 052 053 054 055 056 057 058 059 060 061 062 063 064 065 066 067 068 069 070 071 072 073 074 075 076 077 078 079 080 081 082 083 084 085 086 087 088 089 090 091 092 093 094 095 096 097 098 099 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168

Weekly	See here for weekly puzzles.

Hidden Door	???

Puzzle Index: CV · DB · UF · LS · MM · AL · VS

FANDOM

Puzzle

Hints

Solution

Incorrect

Correct