Question

Find the missing number 15,?,30 ,45

Answer 1

$Given \: sequence : 15,\red{?} , 30, 45$

/* Observe the sequence ,we can find the following pattern */

$First \:term = 15$

$\red{ Second \:term } \\= 15 + \blue { 5 } \\= \red{ 20 }$

$Third \:term \\= 20 + 2\times \blue { 5 } \\=20 + 10 \\= \blue{ 30 }$

$Fourth\:term \\= 30 + 3\times \blue { 5 } \\=30 + 15 \\= \blue{ 45 }$

Therefore.,

$\red{ Missing \: number } \green { = 20}$

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