A recipe for learning

A recipe for learning anything: fifteen minutes a day, five days a week, for four weeks.

A recipe for learning anything: $15$ min a day, $5$ days a week, $4$ weeks.

$15^{\prime }\times 5\times 4$.

Ingredients: a quiet table, a pencil, a timer and one small thing to practise. Method: set the timer for fifteen minutes. Practise only that one thing until the timer rings, then stop, even if you want to carry on.

You need: a quiet table, pencil, timer, $1$ small thing. Set the timer for $15$ min; practise only that thing; stop when it rings.

$1$ thing, timer $15^{\prime }$, then stop.

After one week you have practised seventy-five minutes. After four weeks you have practised three hundred minutes, which is five hours.

Week: $15\times 5=75$ min. Month: $75\times 4=300$ min, and $300÷60=5$ hours.

$15^{\prime }\times 5=75^{\prime }$ and $75^{\prime }\times 4=300^{\prime }$, so $300÷60=5$ hours.

Surprise: five hours is about one long evening. But five hours spread over four weeks stick better, because memory needs sleep between practices. The two days of rest each week are part of the recipe.

$5$ hours is one long evening, but spread over $4$ weeks it sticks better, because memory needs sleep. Rest days: $7-5=2$ a week, part of the recipe.

Spread $S$, cram $C$: $S>C$, memory needs sleep. Rest: $7-5=2$.