12 is first one 7 is 2nd one 9 is the last one
A ratio of 5:7 means out of 12 books, 5 are in one category and 7 are in another. (The “category” isn’t specified in this problem.)
So here we’re STARTING with 36 books; we want to find a ratio that is equal to 5:7 and adds up to 36. Well 36 = 3(12), and so if we multiply each number in the ratio by 3 as well, we might get what we want. Doing that gives us 15:21, which adds up to 36 and is equal to 5:7. Boom, that’s the answer.
P.S. Here’s a question you can think about: why do ratios stay the same when you multiply each number by the same amount? (For example, why is 3:1 the same as 6:2?)
No it is not because you can't make it into a fraction.
Answer:
m∠DRM = 45°
Step-by-step explanation:
∵ PSTR is a parallelogram
∴ TS // RP ⇒ opposite sides
∴ m∠T + m∠R = 180° ⇒ (1) (interior supplementary angles)
∵ m∠T : m∠R = 1 : 3
∴ m∠R = 3 m∠T ⇒ (2)
- Substitute (2) in (1)
∴ m∠T + 3 m∠T = 180
∴ 4 m∠T = 180
∴ m∠T = 180 ÷ 4 = 45°
∴ m∠R = 3 × 45 = 135°
∵ m∠R = m∠S ⇒ opposite angles in a parallelogram
∴ m∠S = 135°
∵ RD ⊥ PS
∴ m∠RDS = 90°
∵ RM ⊥ ST
∴ m∠RMS = 90°
- In quadrilateral RMSD
∵ m∠S = 135°
∵ m∠RDS = 90°
∵ m∠RMS = 90°
∵ The sum of measure of the angles of RMSD = 360°
∴ m∠DRM = 360 - ( 135 + 90 + 90) = 45°
