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# Health Application: A doctor reports blood pressure in millimetres of mercury (mm Hg) as a ratio of systolic blood pressure to diastolic blood pressure (such as 140 over 80). Systolic pressure is measured when the heart beats, and diastolic pressure is measured when it rests. Refer to the table of blood pressure ranges for adults.

Manohar is a healthy 37 years old man whose blood pressure is in the normal category.

(a) Calculate an approximate ratio of systolic to diastolic blood pressures in the normal range. (b) If Manohar’s systolic blood pressure is 102 mm Hg, use the ratio from part (a) to predict his diastolic blood pressure.

(c) Calculate ratio of average systolic to average diastolic blood pressure in the prehypertension category.

**Solution:**

Given, Manohar is a healthy 37 years old man whose blood pressure is in the normal category.

(a) We have to calculate an approximate ratio of systolic to diastolic blood pressures in the normal range.

Normal range from the table,

Systolic blood pressure = 120 mm Hg

Diastolic blood pressure = 80 mm Hg

Ratio of systolic to diastolic blood pressures in the normal range = 120/80

= 12/8

= 3/2

Therefore, the required ratio is 3 : 2

(b) We have to use the ratio from part (a) to predict his diastolic blood pressure, if Manohar’s systolic blood pressure is 102 mm Hg.

Manohar’s systolic blood pressure = 102 mm Hg

Manohar’s diastolic blood pressure = a mm Hg

According to the question,

102/a = 3/2

102 = 3a/2

3a = 102(2)

3a = 204

a = 204/3

a = 68 mm Hg

Therefore, the diastolic blood pressure range of Manohar is 68 mm Hg.

(c) We have to find the ratio of average systolic to average diastolic blood pressure in the prehypertension category.

Average systolic blood pressure in prehypertension category = (120+139)/2

= 259/2 mm Hg

Average diastolic blood pressure in prehypertension category = (80+89)/2

= 169/2 mm Hg

Ratio of average systolic to average diastolic blood pressures = 259/2 : 169/2

= 259 : 169

Therefore, the required ratio is 259 : 169

**✦ Try This: **A sum of money lent out at simple interest amounts Rs 720 after 2 years and to Rs 1020 after a further period of 5 years. What is the sum ?

**☛ Also Check: **NCERT Solutions for Class 7 Maths Chapter 8

**NCERT Exemplar Class 7 Maths Chapter 7 Problem 116**

## Health Application: A doctor reports blood pressure in millimetres of mercury (mm Hg) as a ratio of systolic blood pressure to diastolic blood pressure (such as 140 over 80). Systolic pressure is measured when the heart beats, and diastolic pressure is measured when it rests. Refer to the table of blood pressure ranges for adults.

**Summary:**

Manohar is a healthy 37 years old man whose blood pressure is in the normal category. (a) An approximate ratio of systolic to diastolic blood pressures in the normal range is 3 : 2, (b) If Manohar’s systolic blood pressure is 102 mm Hg, using the ratio from part (a) to predict his diastolic blood pressure, is 68 mm Hg, (c) The ratio of average systolic to average diastolic blood pressure in the prehypertension category is 259 : 169

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