Instructions: type the correct answer in the box. use numerals instead of words. if necessary, use / for the fraction bar.

ab is parallel to cd, and ef is perpendicular to ab

the number of 90° angles formed by the intersections of ef and the two parallel lines ab and cd is

From the diagram, we see that if PQ and RS are parallel and line PR and QS is perpendicular to RS, then the length of PR equals to QS, which mean the ratio is 1:1

The answer is 8 angles.

Step-by-step explanation: As given in the question and shown in the attached figure, AB and CD are two straight lines which are parallel to each other.

Also, another line EF is there which is perpendicular to AB. Now, since AB is parallel to CD, so EF will be perpendicular to CD also.

Therefore, number of 90° angles formed by the intersection of EF and AB is 4, which are ∠1, ∠2, ∠3, ∠4 and number of 90° angles formed by the intersection of EF and CD is also 4 which are ∠5, ∠6, ∠7, ∠8. Please see the attached figure.

Hence, the total number of 90° angles formed = 4 + 4 = 8.

Thus, the answer is 8.

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step-by-step explanatio89