TomB
Hi
1) He runs QUICKER than jacob (wrong)
A) He runs more quickly than jacob
Here "QUICKER" is wrong as it describes "runs" (verb) . so "quickly" (adverb) is correct.
2) He runs faster than jacob.
here "faster " is correct.
How to know whether adverb ending LY or ER IS correct farm? how to know the particular comparitive farm is adjective or adverb?
Fast is an interesting adjective/adverb. "I am a fast runner." Here fast describes the noun 'runner' so it is an adjective. "I run fast." Here fast describes how I run, therefore it is an adverb. As you see here, not all adverbs have an 'ly'. The 'ly' rule for adverbs is a nice generalization, but there are irregularities.
When the GMAT tests adjective vs. adverb, the choices will be pretty straightforward: the species grew quicker (incorrect) vs. the species grew more quickly (correct). They would not give you an option where you would be choosing between quickly and fast.
To determine if something is an adverb/adjective, ask yourself if the word answer the question 'How?' - Adverb or "Which one?" - Adjective. To illustrate:
He drove quickly to arrive at work on time. Here quickly tells us how he drove: Adverb.
The quick driver arrived at work on time. Here quick tells us which driver got to work on time: Adjective.
KW