The answer is 20.

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Since there are five pipes of equal radius initially, the continuity equation can be written

$5 A_1 v_1 = A_2 v_2.$

The problem gives $r_2 = 10r_1$ , so

$5\pi r_1^2 v_1 = \pi (10r_1)^2 v$

$5 r_1^2 v_1 = 100 r_1^2 v$

$v_1 = 20v.$