Power of a convex lens of focal length 40 cm in contact with a concave lens of focal length 25 cm

The same question, asked 2 times: 10 May 2023 S2, 16 May 2023 S2. Every wording below, oldest first.

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Question 1
10 May 2023 S2
14 $A convex lens of focal length 40 cm is in contact with a concave lens of focal length 25 cm. The power of combination is$
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Question 2
16 May 2023 S2
8 $An optician makes spectacles having a combination of a convex lens of focal length 40 cm in contact with a concave lens of focal length 25 cm. The power of this combination of lenses in dioptre is$
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