Why isn't the answer to TMUA-P1-MSTAT-009 shown upfront?

The options are lettered without marking the correct one so you attempt TMUA-P1-MSTAT-009 first — TMUA questions reward spotting the trap before you check the worked solution below.

Do I need a calculator for TMUA-P1-MSTAT-009?

No — calculators are banned in the TMUA. TMUA-P1-MSTAT-009 is set for a no-calculator target of about 150 seconds; the worked solution shows the fastest by-hand route.

Which TMUA specification point is TMUA-P1-MSTAT-009?

TMUA-P1-MSTAT-009 is Paper P1 · Statistics and probability (specification code M-Stat), level 2. Drill more of the same topic from this page.

TMUA-P1-MSTAT-009 — Paper P1 · Statistics and probability · Level 2

P1M-StatLevel 2~150s target

Spec: M-Stat · No calculator · ~150s

The probability it rains on any given day is

0.2

, independently. What is the probability it stays dry on both Saturday and Sunday?

Options

$0.04$
$0.36$
$0.64$
$0.6$
$0.96$

Letters only — the answer key is hidden. Work it out, then check the solution below.

Hint (check trope)

No written hint yet — check the trope: mprob-tree, tree-probability, complement-trap. Name the trap first, work the stem by hand, then open the solution below.

Show solution

P(\text{dry}) = 1 - 0.2 = 0.8

each day, independently, so

P(\text{both dry}) = 0.8^2 = 0.64

. Switch to the complement before multiplying.
Trap:

0.04

multiplies the rain probabilities — that is

P(\text{rain both days})

, the wrong branch.

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Keep practising

Same topic · same level

P1M-StatLevel 2

TMUA-P1-MSTAT-001

Two fair six-sided dice are rolled. What is the probability that the total is 9?

Statistics and probability

Open TMUA-P1-MSTAT-001 →

Same trap: tree-probability

P1M-StatLevel 2

TMUA-P1-MSTAT-004

The probability it rains on any given day is 0.3, independently. What is the probability it stays dry on both Saturday a…

Statistics and probability

Open TMUA-P1-MSTAT-004 →

Step up a level

P1M-StatLevel 3

TMUA-P1-MSTAT-006

1 in 10 people carries a trait. A test is 90\% accurate both ways (true-positive and true-negative rates are 0.9 ). Give…

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Open TMUA-P1-MSTAT-006 →

TMUA-P1-MSTAT-009 — Paper P1 · Statistics and probability · Level 2

Options

Keep practising

Master Statistics and probability

TMUA-P1-MSTAT-009 — Paper P1 · Statistics and probability · Level 2

Options

Keep practising

Master Statistics and probability