closest benchmark on a number line
Fraction Observatory
A proper fraction appears in large type under the words Aim at the closest benchmark. You press the star for 0, ½, or 1, and the telescope turns toward that star. A correct star marks the fraction on the number line and shows how far it sits from each benchmark. The last three rounds change the task to Which fraction is greater?
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How to Play Fraction Observatory
- 1
Aim at the closest benchmark
The task line says Aim at the closest benchmark, and the fraction appears in large type. Press the star 0, ½, or 1 while feedback says Choose a benchmark.
- 2
Try another benchmark
If that star is not the closest, the message changes to Try another benchmark and the same fraction stays. When you press the closest star, the fraction is marked on the line and the three distances appear.
- 3
Which fraction is greater?
On rounds 13 to 15 the task changes to Which fraction is greater? Press the greater fraction, or the message reads Try the other fraction.
- 4
Next star
Press Next star to move the pill from 1 / 15 toward 15 / 15. After that press on the last star, the task says All stars found! and the button says Play again.
Key Features
Three benchmark stars
The rail has three stars labeled 0, ½, and 1. Press a star and the telescope turns to it, while feedback reads Choose a benchmark.
Highlighted closest distance
A correct star places the fraction on the number line and writes how it compares with ½, using <, =, or >. Three subtraction lines share a denominator of twice the fraction's denominator, and the shortest line is highlighted.
Two fractions on the line
Rounds 13 to 15 hide the clickable stars and show 0, ½, and 1 as fixed marks, with two fraction buttons on the line. The task reads Which fraction is greater?, and the smaller button brings the message Try the other fraction.
Pill from 1 / 15 to 15 / 15
The header pill counts the round from 1 / 15 through 15 / 15, and Next star appears only after a correct choice. Pressing Next star on round 15 hides the number line, sets the task to All stars found!, and changes the button to Play again.
What is Fraction Observatory?
Fraction Observatory puts proper fractions on a number line whose benchmarks are 0, ½, and 1. For twelve rounds you name the closest benchmark. For three rounds you choose the greater of two fractions by which side of ½ it sits on. For 3/8 the screen uses denominator 16. It shows 0 → 6/16 - 0/16 = 6/16, ½ → 8/16 - 6/16 = 2/16, and 1 → 16/16 - 6/16 = 10/16. The highlighted line is ½, and the result reads 3/8 < ½ with the star ½.
Why Play Fraction Observatory?
- 1
Four fractions for each benchmark
Each game takes four fractions whose closest benchmark is 0, four whose closest is ½, and four whose closest is 1. Those twelve are shuffled before the comparisons begin.
- 2
Wrong press, same round
Try another benchmark leaves the fraction in place, and Try the other fraction leaves the pair in place. The pill advances only after a correct choice, when you press Next star.
- 3
Twice the denominator
Every gap is a subtraction whose denominator is twice the fraction's denominator. For 7/8 that denominator is 16, the highlighted gap is 2/16, and the star is 1.
- 4
Two fixed comparison lists
One fraction is chosen from 1/3, 2/6, 3/8, 3/9, 4/11, or 4/12, and the other from 2/3, 4/6, 5/8, 6/9, 7/11, or 8/12. The greater fraction is the one above ½, and a correct press writes both around ½, as in 3/8 < ½ < 5/8.
Frequently Asked Questions
How many rounds are in one game?
Fifteen. The first twelve ask for the closest benchmark: four fractions for 0, four for ½, and four for 1, in shuffled order. The last three ask Which fraction is greater? The pill shows the place, from 1 / 15 to 15 / 15.
What happens on a wrong press?
On a benchmark round the telescope still turns to the star you pressed, and the message changes to Try another benchmark. On a comparison round it turns to the fraction you pressed, and the smaller one shows Try the other fraction. The pill stays on that round until the correct choice, then Next star.
How is the distance for 3/8 shown?
The game rewrites 0, ½, 1, and 3/8 with denominator 16. The lines are 0 → 6/16 - 0/16 = 6/16, ½ → 8/16 - 6/16 = 2/16, and 1 → 16/16 - 6/16 = 10/16. The 2/16 line is highlighted, and the result reads 3/8 < ½ with the star ½.
Which fractions appear, and which are left out?
Denominators run from 3 through 12, and numerators run from 1 to one less than the denominator. Six fractions are left out because two benchmarks are the same distance away: 1/4, 2/8, and 3/12 tie between 0 and ½, and 3/4, 6/8, and 9/12 tie between ½ and 1. Fractions equal to ½ can be chosen for that star: 2/4, 3/6, 4/8, 5/10, and 6/12. Their result line uses =, as in 4/8 = ½.
What happens when every star is found?
Press Next star after the 15th correct choice. The number line hides, the task says All stars found!, and the button says Play again. Play again builds a new shuffle of twelve benchmark rounds and three comparisons. The Sound button turns the music on or off, and the browser remembers that choice.
