10-Second Challenge
The Lying Jack-o’-Lantern
On Halloween night, four jack-o’-lanterns tell some trick-or-treaters their heights and the lengths of their shadows. They’re standing on the same level ground under the same moonlight—but one is lying.
Which one is lying?
Show the solution
Jack-o’-lantern B is lying!
Under the same moonlight, the jack-o’-lanterns and their shadows form similar triangles, so their height-to-shadow ratios must match.
Jack-o’-lanterns A, C, and D all have shadows twice their heights. But B claims to be 13 inches tall with a 25-inch shadow. Its shadow should be 26 inches long.
One inch gave the liar away.