Convert the Otter Matches the Units

Sliding happily between the yard pool and the metre pool is Convert, a sleek river otter who is never fooled by a shorter lane. Otters swim in any water, and Convert swims between two worlds — yards and metres — and knows the secret that keeps comparisons honest.

A young swimmer came bursting with news. “I swam 100 yards in 1:05, and last month I did 100 metres in 1:07. I got faster!” Convert paused mid-glide. “Did you, though?” he asked kindly. “A yard is a little shorter than a metre — about 0.914 of one. So a 100-yard pool is shorter than a 100-metre pool. Of course the shorter swim took less time. You compared two different distances.”

He showed the fix. “Before you compare, convert them to the same unit. 100 yards is about 91.4 metres — so your 1:05 was for a shorter swim. To compare fairly, we’d scale it up to a full 100 metres.” He worked it through gently, never making her feel foolish for the honest mix-up — it catches even fast swimmers. “Once both are in metres, then the times mean the same thing, and you can see who really improved.”

Say it with Convert, out loud: “A yard’s a touch shorter than a metre, you’ll find — convert first, keep the units aligned.”

She redid the comparison in matching units, and the picture came out true — a little different from what she’d hoped, but real. “At least now it’s honest,” she said. Convert twirled in the water. “Honest is the only kind of faster worth having.”

That is Convert’s move. A yard is a bit shorter than a metre, so times from a yard pool and a metre pool don’t compare straight across. Convert both to the same unit first — then, and only then, the numbers tell the truth.