Why 'really good' isn't correct in Sasha's chemistry sentence and how to use 'well' instead.

How a Tiny Word Slip Can Swing a Whole Sentence — and What It Teaches Us About PACT-style Items

grammar is one of those everyday tools that sneaks up on you. You think you’ve nailed it, then a sentence shows up that trips you up just enough to make you pause. If you’re digging into PACT-style sentence questions, a small detail can be the difference between getting it right and getting it wrong. Let me walk you through one classic snag you’ll see again and again: choosing the right word form after a doing verb.

The sample that trips readers up

Here’s a sentence you might encounter in a PACT-like item:

Sasha was doing really good in chemistry this semester because she studied her chemistry notes every night.

And here are the answer options you’d usually see:

A. really good

B. semester because

C. homework assignments,

D. Mr. Homer’s tutorials.

The correct answer? A: really good.

That’s the line that needs adjustment. But why is that the correct pick? Let’s unpack it.

What’s wrong with “really good”?

At first glance, “really good” sounds natural in everyday speech. We often say “That’s really good!” in casual talk, right? But in this particular sentence, the word after “doing” needs to describe the action Sasha is performing, not her internal state or the quality of some thing she possesses. In other words, “doing” is an action word here, and the adverb that follows should describe how she performed that action.

In standard usage, when you describe performance in an action, you use the adverb form that attaches to the verb—“doing well.” The phrase “really well” tells us that Sasha performed the act of studying and working in a successful way. “Really good” would be describing Sasha as a person or her character in a way that doesn’t fit the action of “doing.”

Put plainly: “Sasha was doing really well in chemistry this semester…” communicates that her performance was strong. “Sasha was doing really good…” risks implying something more about her state or character, or it just sounds off to careful readers who expect the adverb to modify the verb.

The rule in plain English

• After an action verb (like doing, running, solving, writing), the adverb typically modifies the verb. The standard form is often an adverb that describes how the action was carried out.

• The conventional adverb form for “good” when attached to an action is “well,” not “good.” So you say “do well,” not “do good.”

• The word “really” can intensify an adverb (really well) or an adjective (really good). The key is to pair it with the correct word class for the context. In this sentence, the correct pairing is “really well.”

A quick contrast you can keep in your back pocket

• Sasha was doing well in chemistry this semester. (Correct: describes performance)

• Sasha was doing good in chemistry this semester. (Usually considered incorrect here because “good” is an adjective, not an adverb describing the action)

• Sasha did really well on the test. (Another natural, correct construction, focusing on the action and its result)

Why the other options aren’t the fix

Let’s briefly inspect why the other choices aren’t the correction:

• B. “semester because” — This isn’t addressing the core grammatical snag. The sentence can flow with a proper causal connection, but the error isn’t about the conjunction or the clause structure; it’s about the word form after the doing verb.

• C. “homework assignments,” — This fragment doesn’t complete the thought and doesn’t address the adverb/adjective issue at all. It’s a content mismatch, not a form mismatch.

• D. “Mr. Homer’s tutorials.” — This is just a different ending, not a fix to the problem at hand. It changes the subject or the supporting material, but the error flagged by the question sits in the “really good” phrase.

How to approach similar items on PACT-style checks

Think like a grammar detective, and you’ll move quickly from hesitation to clarity. Here’s a simple, repeatable approach:

1. Identify what the word is trying to modify. If the sentence says someone is “doing” something, ask: what word directly follows to describe that action? If it’s an adjective, you’ve probably got the wrong form.

2. Check the verb-adverb pairing. Action verbs pair naturally with adverbs (how the action is performed). If you see “do” or “is doing” followed by an adjective, pause and test the adverb form.

3. Test the sense you want to convey. Do you mean performance (doing well) or state/mquality (being good)? Choose the word that preserves that meaning.

A couple more quick examples to test the idea

• Maria was running really slow this morning after the long shift. (Try: “running really slowly”)

• They were solving really difficult problems last night. (This one’s tricky: “difficult” modifies problems, which is allowed; if you want to emphasize the action, “solving very difficult problems” is okay, but here “really difficult” is optional for emphasis, not a grammar error)

• The team performed really good in the exhibition game. (Fix: “performed really well”)

If you’re staring at a sentence and you’re unsure whether the issue is a verb-adverb pairing or something else, a quick swap test helps. Replace the word after the doing verb with the adverb form you suspect (well, slowly, carefully, etc.). If the sentence sounds clunky or means something different, you’ve likely found the right fix.

Why this matters beyond the test

Grammar isn’t about being pedantic; it’s about clear communication. In real-life writing—emails, notes, short essays, even social media captions—getting these tiny choices right matters. It signals that you know how language functions, and it helps your reader focus on your ideas rather than on squinting at a sentence to make sense of it.

If you enjoy a little linguistic curiosity, you’ll notice this rule shows up in everyday speech, too. People often say “I did good,” and while many native speakers use that casually, in formal writing or careful reading contexts, you’ll want the adverbial form that aligns with the action. The more you notice these patterns, the more confident you’ll feel when you encounter them in tests—or in real life.

A light touch of strategy for steady improvement

• Read sentences aloud when you’re unsure. If your ear catches an odd cadence, there’s a strong chance something is off.

• When editing, circle the word immediately following a doing verb. If it’s an adjective, try an adverb form and see if it improves the flow.

• Remember that “well” and “good” aren’t interchangeable in every situation. The key is what word class they belong to in the sentence and how they relate to the verb.

A few quick practice prompts (no pressure—these are just for understanding)

• Jonah was painting really ____ this morning. (Possible options: well, good)

Answer: well. Explanation: painting is an action; use the adverb form to describe how the action was performed.

• The coach noted that the players played ____ this season. (Options: well, good)

Answer: well. Explanation: “played” is a verb; describe how the playing occurred.

• She feels really ____ about the project. (Options: well, good)

Answer: good. Explanation: here “good” describes her state of feeling, which is why it’s an adjective after the linking verb feel.

Bringing it all together

Here’s the bottom line: in sentences that center on an action, the right adverb helps your meaning shine through. When you see the problem phrase “really good” after a doing verb like “was doing,” the fix is usually to switch to “really well.” It’s a small tweak with a big payoff for clarity.

If you’re exploring PACT-style items with an eye on accuracy, this kind of decision tree—what is being modified, by whom, and how—will become second nature. The more you practice this kind of linguistic detective work, the easier it becomes to spot not just the obvious errors but the subtler ones too. And the better you get, the more confident you’ll feel about your everyday writing as well as your test-ready reading of sentences.

A quick note on tone and flow

As you practice, aim for a balance: clear, precise explanations that stay close to the point, seasoned with a touch of everyday language that keeps you engaged. Think of the reader as someone who values both accuracy and accessibility—someone who wants to understand why a sentence works the way it does, not just what to change. That blend makes your writing approachable, memorable, and useful far beyond any one test.

Final takeaway

The example with Sasha isn’t just about picking one erroneous phrase. It’s a compact lesson in how choosing the right form—well over good—shapes meaning and reader perception. Nail that distinction, and you’ll be well on your way to handling similar items smoothly, with a sense of confidence rather than hesitation. And as you keep exploring, you’ll find that grammar, when treated with curiosity and care, can be a surprisingly enjoyable part of everyday writing.