In a healthy adult human at rest, what is considered the normal arterial blood pressure (systolic/diastolic) measured in millimetres of mercury (mmHg)?

Introduction / Context:
Blood pressure is a key vital sign that reflects the force of blood against the walls of arteries as the heart pumps. It is usually expressed as systolic pressure over diastolic pressure, measured in millimetres of mercury (mmHg). Knowing the typical normal value for a healthy adult at rest is important both for general health awareness and exam preparation. This question asks you to identify that standard normal value.

Given Data / Assumptions:

We are considering an average healthy adult at rest, not a child or an athlete. Blood pressure is given as systolic/diastolic in mmHg. Options include common approximate values such as 120/80 mmHg and others. We assume standard clinical guidelines used in introductory physiology.

Concept / Approach:
Systolic pressure is the higher value, measured when the heart's ventricles contract and eject blood into the arteries. Diastolic pressure is the lower value, recorded when the ventricles relax and the heart refills. For a typical healthy adult at rest, the normal arterial blood pressure is often quoted as around 120/80 mmHg. Although individual values can vary slightly, and modern guidelines may refine what counts as optimal, 120/80 remains the classic textbook example and is widely used in general knowledge questions.

Step-by-Step Solution:
Step 1: Recall the standard textbook value for normal blood pressure: approximately 120/80 mmHg. Step 2: Recognise that the first number represents systolic pressure and should be higher than the diastolic pressure. Step 3: Examine option a (80/120), which reverses the order and places a lower value first, making it incorrect. Step 4: Check other options like 80/110 and 110/90, which may occur in some individuals but are not the standard reference values. Step 5: Confirm that 120/80 mmHg, with a higher systolic and lower diastolic number, matches the widely accepted normal reference.

Verification / Alternative check:
You can verify by recalling how blood pressure readings are written in medical reports and health articles. Whenever normal blood pressure is mentioned, 120/80 mmHg is given as the typical example. Health education posters and school textbooks also highlight this number when teaching about hypertension and hypotension. While there is a range of normal values, and guidelines may discuss ideal lower targets, for exam purposes 120/80 mmHg is the expected answer and the only option that fits the classic pattern.

Why Other Options Are Wrong:
Option a (80/120 mmHg) reverses systolic and diastolic values, which is physiologically incorrect because systolic pressure should be higher. Option c (80/110 mmHg) and option d (110/90 mmHg) represent possible readings but are not the standard normal adult reference. Option e (100/60 mmHg) may be seen in some healthy individuals, especially athletes, but again is not the typical textbook value quoted as normal for the general adult population. Therefore, these alternatives do not match the established normal reference of 120/80 mmHg.

Common Pitfalls:
A common mistake is to confuse the order of systolic and diastolic pressures or to assume that any combination of two plausible numbers could be called normal. Another pitfall is to overthink small variations and forget that exams usually expect the standard textbook value. To avoid these errors, remember the mnemonic that the higher number (about 120) is systolic and comes first, while the lower number (about 80) is diastolic and comes second. This simple pattern reinforces 120/80 mmHg as the classic normal blood pressure reading.

Final Answer:
The normal arterial blood pressure in a healthy adult human at rest is approximately 120/80 mmHg.