40 questions with worked solutions. Multiple choice at the level of the Mathematics Admissions Test: algebra, calculus, sequences, trigonometry and counting.
Complete the square: (x−3)2+4. The square is at least 0, so the minimum is 4, at x=3.
2MediumMAT
k=1∑99k(k+1)1=
9998
10099
1
101100
100101
Show answer
Answer: B. 10099
Partial fractions: k(k+1)1=k1−k+11. The sum telescopes to 1−1001.
3MediumMAT
How many real roots does x3−3x+1=0 have?
0
1
2
3
4
Show answer
Answer: D. 3
f′(x)=3x2−3 vanishes at x=±1. f(−1)=3>0 and f(1)=−1<0, and f→∓∞ as x→∓∞. So f crosses zero once before −1, once in (−1,1) and once after 1.
4MediumMAT
∫01xexdx=
1
e−1
2e
2
e
Show answer
Answer: A. 1
By parts with u=x, dv=exdx: [xex]01−∫01exdx=e−(e−1)=1.
5MediumMAT
The line y=mx is tangent to the circle (x−4)2+y2=4. What is m2?
41
31
21
32
43
Show answer
Answer: B. 31
Tangency means the distance from the centre (4,0) to the line mx−y=0 equals the radius: m2+1∣4m∣=2. So 16m2=4m2+4 and m2=31.
6MediumMAT
For how many integers n with 1≤n≤100 is n2+n divisible by 6?
33
50
66
67
100
Show answer
Answer: C. 66
n(n+1) is always even, so we need 3∣n(n+1): n≡0 or 2(mod3). There are 33 of each in the range (3 to 99 and 2 to 98), so 66.
7EasyMAT
log23⋅log34⋅log45⋯log6364=
3
4
5
6
7
Show answer
Answer: D. 6
Change of base: logab=lnalnb. The product telescopes to ln2ln64=log264=6.
8EasyMAT
What is the area of the region enclosed by y=x2 and y=2x?
32
1
34
23
38
Show answer
Answer: C. 34
The curves meet at x=0 and x=2, with the line above. ∫02(2x−x2)dx=4−38=34.
9MediumMAT
What is the remainder when x100 is divided by x2−1?
0
1
x
x+1
100x
Show answer
Answer: B. 1
Write x100=(x2−1)q(x)+ax+b. At x=1: 1=a+b. At x=−1: 1=−a+b. So a=0, b=1.
10MediumMAT
How many solutions does 2sin2x+3cosx=3 have with 0≤x<2π?
1
2
3
4
6
Show answer
Answer: C. 3
Use sin2x=1−cos2x: 2cos2x−3cosx+1=0, so cosx=1 or 21. cosx=1 gives x=0; cosx=21 gives 3π and 35π. Three solutions.
11EasyMAT
For how many real values of k does x2+kx+k=0 have a repeated root?
0
1
2
3
Infinitely many
Show answer
Answer: C. 2
Repeated root iff the discriminant k2−4k=0: k=0 or k=4.
12EasyMAT
What is the coefficient of x3 in the expansion of (1+2x)6?
20
80
120
160
240
Show answer
Answer: D. 160
(36)(2x)3=20⋅8x3=160x3.
13MediumMAT
1+32+93+274+⋯=
23
2
49
3
827
Show answer
Answer: C. 49
This is ∑n≥0(n+1)rn with r=31. Differentiating ∑rn=1−r1 gives ∑(n+1)rn=(1−r)21=49.
14EasyMAT
In how many distinct ways can the letters of OXFORD be arranged?
60
120
180
360
720
Show answer
Answer: D. 360
Six letters with O repeated twice: 2!6!=360.
15EasyMAT
What is the largest value of sinx+3cosx?
1
2
3
2
1+3
Show answer
Answer: D. 2
sinx+3cosx=2sin(x+3π), with maximum 2. The two terms cannot both be at their maximum at once, so 1+3 is too big.
16EasyMAT
What is the local maximum value of f(x)=x3−6x2+9x?
0
4
6
9
18
Show answer
Answer: B. 4
f′(x)=3(x−1)(x−3); f′′(1)=−6<0, so the maximum is at x=1: f(1)=4.
17EasyMAT
How many real numbers x satisfy ∣x2−4∣=3?
0
2
3
4
6
Show answer
Answer: D. 4
x2−4=3 gives x=±7; x2−4=−3 gives x=±1. Four solutions.
18EasyMAT
If a>0 and ∫0a(2x−1)dx=6, then a=
2
6
3
4
6
Show answer
Answer: C. 3
a2−a=6, so (a−3)(a+2)=0 and a=3.
19EasyMAT
The circles x2+y2=1 and (x−3)2+(y−4)2=r2 touch externally. What is r?
2
3
4
5
6
Show answer
Answer: C. 4
The centres are 5 apart. External tangency means 1+r=5, so r=4.
20EasyMAT
How many of the numbers 210, 37, 54, 103 are greater than 1000?
0
1
2
3
4
Show answer
Answer: C. 2
210=1024 and 37=2187 exceed 1000; 54=625 does not, and 103=1000 is not greater than 1000.
21MediumMAT
What is the smallest positive integer n for which n! is divisible by 1000?
10
12
15
20
25
Show answer
Answer: C. 15
1000=23⋅53. Factors of 2 are plentiful; the fives come from 5, 10, 15. So n=15 (14! has only two).
22MediumMAT
A sequence has a1=1 and an+1=1+anan. What is a100?
2991
1011
1001
991
100
Show answer
Answer: C. 1001
Take reciprocals: an+11=an1+1. So an1=n and a100=1001.
23EasyMAT
For which value of k is x2+y2−4x+6y=k a circle of radius 5?
−12
5
12
13
25
Show answer
Answer: C. 12
Complete the squares: (x−2)2+(y+3)2=k+13. Radius 5 needs k+13=25, so k=12.
24MediumMAT
What is the maximum value of x2+1x over real x?
41
31
21
1
There is no maximum
Show answer
Answer: C. 21
For x>0, AM–GM gives x2+1≥2x, so x2+1x≤21, with equality at x=1. Negative x give negative values.
25EasyMAT
How many integers n with 1≤n≤100 have n2 ending in the digit 1?
10
20
25
40
50
Show answer
Answer: B. 20
A square ends in 1 exactly when the number ends in 1 or 9: ten of each in the range.
26MediumMAT
What is the coefficient of x2 in (1+x+x2)3?
3
6
9
12
27
Show answer
Answer: B. 6
Take x2 from one bracket and 1 from the others (3 ways), or x from two brackets (3 ways): 3+3=6.
27MediumMAT
What is the smallest value of 3sinx+4cosx+5?
0
1
2
5
10
Show answer
Answer: A. 0
3sinx+4cosx=5sin(x+α) with tanα=34, so it ranges over [−5,5] and the sum has minimum 0.
28MediumMAT
How many pairs of real numbers (x,y) satisfy both x2+y2=1 and x+y=1?
0
1
2
3
Infinitely many
Show answer
Answer: C. 2
Substitute y=1−x: 2x2−2x=0, so x=0 or x=1, giving (0,1) and (1,0) — the line is a chord of the circle.
29EasyMAT
∫1exlnxdx=
21
1
e−1
2e
2e2−1
Show answer
Answer: A. 21
With u=lnx the integral is ∫01udu=21.
30MediumMAT
If f(x)=1−xx, what is f(f(x))?
x
1−2xx
1+xx
−x
x1−x
Show answer
Answer: B. 1−2xx
f(f(x))=1−1−xx1−xx=(1−x)−xx=1−2xx.
31MediumMAT
How many real solutions does 2x=x+2 have?
0
1
2
3
Infinitely many
Show answer
Answer: C. 2
Let f(x)=2x−x−2. f(−2)=0.25>0, f(0)=−1<0 and f(2)=0, and f is convex, so the curve meets the line exactly twice: once between −2 and 0, and again at x=2.
32EasyMAT
What is the sum of the roots of x3−6x2+11x−6=0?
−6
1
3
6
11
Show answer
Answer: D. 6
For x3+ax2+bx+c the roots sum to −a, here 6. (They are 1, 2 and 3.)
33MediumMAT
What is the area between y=x1 and the x-axis from x=1 to x=8?
ln2
2ln2
3ln2
ln7
7
Show answer
Answer: C. 3ln2
∫18xdx=ln8=3ln2.
34MediumMAT
How many ways are there to choose three numbers from 1 to 10 so that no two are consecutive?
48
56
64
84
120
Show answer
Answer: B. 56
Subtract 0, 1 and 2 from the three chosen numbers in increasing order: this matches the choices with a bijection to any 3 numbers from 1 to 8, so (38)=56.
35EasyMAT
If loga2=0.3, what is loga8?
0.3
0.6
0.9
2.7
3
Show answer
Answer: C. 0.9
loga8=loga23=3loga2.
36MediumMAT
For which x does 2log3x=log3(2x+3)?
−1
1
3
Both −1 and 3
No solution
Show answer
Answer: C. 3
x2=2x+3 gives x=3 or x=−1, but log3x needs x>0, so only x=3 survives.
37HardMAT
For how many integers n with 1≤n≤10 is n2<2n?
6
7
8
9
10
Show answer
Answer: B. 7
It holds at n=1, fails at n=2,3,4 (where n2≥2n), and holds from n=5 onwards: 1 and 5,…,10, seven values.
38MediumMAT
For how many values of a does the tangent to y=x2 at x=a pass through (0,−1)?
0
1
2
3
Infinitely many
Show answer
Answer: C. 2
The tangent is y=2ax−a2. Through (0,−1): −a2=−1, so a=±1.
39EasyMAT
What is the minimum value of x+x9 for x>0?
4
6
9
12
There is no minimum
Show answer
Answer: B. 6
By AM–GM, x+x9≥29=6, with equality at x=3.
40MediumMAT
How many digits does 2100 have?
30
31
32
33
100
Show answer
Answer: B. 31
log102100=100log102≈30.103, so the number lies between 1030 and 1031: 31 digits.