Five warm-ups for grades 9–12. Each takes three to five minutes. Answers and teacher notes are in the collapsed box under each prompt.
ELA
This sentence is a comma splice. Fix it three different ways: once with a period, once with a semicolon, and once with a comma plus a conjunction.
The bus was late again, most of us missed the start of first period.
Answer and teacher notes
Period: The bus was late again. Most of us missed the start of first period.
Semicolon: The bus was late again; most of us missed the start of first period.
Comma + conjunction: The bus was late again, so most of us missed the start of first period.
A comma splice joins two complete sentences with only a comma. A comma alone can’t hold two independent clauses together. Ask which version best shows that the second idea is caused by the first (the “so” version makes it explicit).
Math
You roll two fair six-sided dice and add the numbers. Which is more likely: a sum of 7 or a sum of 10? Give the probability of each as a fraction in lowest terms.
Answer and teacher notes
There are 6 × 6 = 36 equally likely outcomes.
Sum of 7: (1,6), (2,5), (3,4), (4,3), (5,2), (6,1) = 6 outcomes, so 6/36 = 1/6.
Sum of 10: (4,6), (5,5), (6,4) = 3 outcomes, so 3/36 = 1/12.
A sum of 7 is twice as likely as a sum of 10. Check: 1/6 = 2/12. The most common error is counting (4,6) and (6,4) as the same outcome; on two separate dice they are different.
Science
Natural gas is mostly methane (CH4). When it burns completely, it reacts with oxygen to make carbon dioxide and water. Balance the equation, then prove it is balanced by counting atoms on each side.
__ CH4 + __ O2 → __ CO2 + __ H2O
Answer and teacher notes
CH4 + 2 O2 → CO2 + 2 H2O
Atom count: carbon 1 = 1. Hydrogen 4 = 2 × 2 = 4. Oxygen 2 × 2 = 4 on the left; 2 (in CO2) + 2 × 1 (in water) = 4 on the right. Tip: balance C and H first, then O last, since oxygen shows up in both products. Students who change subscripts (writing H4O) have changed the substance, not balanced it.
Source: U.S. Energy Information Administration: Natural Gas Explained
Social Studies
On this day in 2010, all 33 workers trapped by a collapse at the San José gold and copper mine in Chile’s Atacama Desert were brought to the surface after 69 days underground. Imagine you led the team on the surface. List three problems you would need to solve to keep 33 people alive until a rescue was possible, and rank them from most to least urgent. Explain your top choice.
Answer and teacher notes
Answers will vary. Strong lists include finding out whether anyone survived and where they are, getting air, water, food, and medicine down to them, keeping communication open, protecting their mental health over weeks of waiting, and designing a safe way to lift people up. Reward rankings that are justified (for example, “locating them comes first because nothing else is possible until we know where they are”).
Facts to share afterward: the collapse happened on August 5, 2010, and all 33 were brought up in a specially designed rescue capsule called Phoenix. Quick math: 69 days is just under 10 weeks.
Current Events
NASA reported this week that Antarctic sea ice reached its yearly maximum on September 14, 2026, covering 17.59 million square kilometers. Just two days earlier, on September 12, Arctic sea ice hit its yearly minimum of about 4.6 million square kilometers. (a) Why would one pole’s ice peak in the same week the other pole’s ice is at its lowest? (b) About how many times larger was the Antarctic ice extent than the Arctic’s?
Answer and teacher notes
(a) The hemispheres have opposite seasons because Earth is tilted on its axis. Mid-September is the end of winter in the Southern Hemisphere, after months of cold and darkness let ice build up, and the end of summer in the Northern Hemisphere, after months of sunlight melted it back.
(b) 17.59 ÷ 4.6 ≈ 3.8 times larger. NASA noted that this year’s Antarctic peak was the third-lowest maximum since satellite observations began. Good follow-up: why do scientists compare each year to a long record instead of just to last year?
Sources: NASA Earth Observatory: Antarctic Sea Ice Grows to Its 2026 Maximum; NASA Earth Observatory: Arctic Sea Ice Shrinks to Its 2026 Minimum