# General GRE Math Study

## 56 terms · Customized Flashcards for GRE Math Study. Rules, Theorems, and Tips and Tricks.

### What is the divisibility rule for 2?

The last digit must end in 0, 2, 4, 6, or 8.

### What is the divisibility rule for 3?

Sum all digits and divide by 3.

### What is the divisibility rule for 4?

Divide the last two digits by 4.

### What is the divisibility rule for 5?

The last digit ends in 0 or 5.

### What is the divisibility rule for 6?

The number is divisible by 2 and 3.

No simple rule.

### What is the divisibility rule for 8?

Divide the last 3 digits by 8.

### What is the divisibility rule for 9?

Sum the digits of the number and divide by 9.

121

144

169

196

225

256

289

324

361

400

o + o = e
e + e = e
e + o = o

o * o = o
e * (o or e) = e

≈ 1.4

≈ 1.7

≈ 2.2

≈ 3.14

≈ 2.7

### What is the sum of consecutive even integers?

n(n+1), where n = the number of terms.

### What is the sum of consecutive odd integers?

n^2, where n = the number of terms.

### What is the sum of consecutive integers?

[n(n+1)]/2, where n = the number of terms.

(n-m)+1

(n-m)/d + 1

### Given the same parameters which is greater combinations or permutations?

With permutations order matters, so they are greater in number than combinations. P(n,r) = n!/(n-r)! and C(n,r) = n!/r!(n-r)!.

### What is the formula for permutations?

P(n,r) = n!/(n-r)!

### What is the formula for combinations?

C(n,r) = n!/r!(n-r)!

25 primes

### Name four common right triangle side triples. ( a, b, c)

(3,4,5), (5,12,13), (1,1,sqrt(2)), (1,sqrt(3),2)

### A triangle with 3 equal sides and 3 equal angles is called?

An equilateral triangle

### A triangle with 2 equal sides and 2 equal angles is called?

An Isoceles triangle

### What is the exterior angle theorem?

The external angle A of triangle ABC is equal to the two opposite interior angles at B and C.

### What is the triangle Inequality theorem?

Any one side of a triangle is less than the sum of the two other sides. a < b + c, b < a + c, c < a+b

### What is the parallel line theorem?

if lines L1 // L2 is transversed by l3, angles 1,4,5,8 are equal and angles 2,3,6,7 are equal.

equal areas

smallest

greatest

[sqrt(3)/2]x

1/2 * (b1 + b2)h

equal

(n - 2)180

360

### How are permutations and combinations related?

C(n,r) = P(n,r) / r!

### What is the sum of an arithmetic progression?

S = n/2[2a * (n-1)d]

(1, sqrt(3), 2)

(1, 1, sqrt(2))

180

90

### What is the sum of an Arithmetic Progression (AP)?

S = n/2[ 2a + (n-1)d]

### What is the value of the nth term of an arithmetic progression?

an= a1 + (n-1)d, where an is the nth term, a1 is first term, and d is the difference.