Here is our first clue: "I have seven hundredths and three tenths."

What could my mystery number be? This is a think-first moment, so just work it out in your head for now. Lots of numbers still fit, because we only know two of the columns so far, so it is fine if you cannot name just one number yet.

You are about to see two different clues built on the place-value mat. Watch which columns each clue fills in, and see if you can spot why the two clues do very different jobs.

Today we work through one full mystery puzzle together, one clue at a time, on the place-value mat. Because this puzzle goes to three decimal places, we add a fourth column, the thousandths, to the right of the hundredths. Each clue tells us about one more column, and rules out every number that does not fit it. Read each clue, build what we know so far, and say what is still open.

• Clue A: I am bigger than 0.5 and smaller than 0.6.
• Clue B: My hundredths digit is 2.
• Clue C: My thousandths digit is 5.

Clue A gives us the tenths column. Clue B and Clue C then fill the smaller columns, one at a time, until the whole number is built. Read it aloud in words to check it sounds right.