show posts with range meta key

Question

You can compare BETWEEN in the meta_query and you need to set the type too for NUMERIC.

For example

$args = array(
'post_type'  => 'my_custom_post_type',
'meta_key'   => 'age',
'orderby'    => 'meta_value_num',
'order'      => 'ASC',
'meta_query' => array(
    array(
        'key'     => 'age',
        'value'   => array( 5, 10 ),
        'compare' => 'BETWEEN',
        'type'    => 'NUMERIC'
    )
));
$query = new WP_Query( $args );